Pre-submission advice:  academic references

Almost all academic publications require references to be provided.  It is important to do this systematically and consistently.  When writing for a journal or conference, you may also need to adopt the preferred style & formatting of the publisher.  

Maintaining your own bibliographic database

Citations in text

Enumeration

Superscripted numbers

Inline numbers

Author & year

Prevalence of various citation styles

List of references

References arranged in order of citation

References arranged in alphabetical order by surname

Spacing of year, volume number, issue number, and page(s)

Prevalence of various reference styles

 

Maintaining your own bibliographic database

Using a bibliographic software application (EndNote, Zotero, Mendeley, RefWorks, BibTeX, Citavi, NoteExpress, etc.) can help to some extent, but the author(s) must also take responsibility to ensure that the data entered into such an application are likewise consistent, no matter how the data are entered: 

  • typing manually (especially for older, print-only resources) allows you to undertake your own due diligence, but is still subject to the prospect of typographical errors;  or 
  • using built-in functionality of advanced software applications to attempt to extract bibliographic metadata from PDF files is known to be quite unreliable — inconsistent, and sometimes highly inaccurate;  or 
  • downloading from an online source is no guarantee of accuracy, as there are many instances of records in online databases containing a variety of errors — 
    • even the publisher's own website can include misprints (usually data-entry errors for newer works, but sometimes OCR errors for older works), 
    • secondary tools (like Google Scholar) can perpetuate those misprints as well as introducing new errors (such as when they attempt to automatically parse PDF files found online or when they rely on scanning lists of cited references), and
    • in both cases it is common to see
      • spurious specification of the date of publication being the first of January (usually because the true day and month were not specified, but the computer system required values to be entered, so fictional default values of "1" were entered for each), and
      • poor/erratic handling of ligatures (e.g. ӕ, ffi, st), accented or embellished characters (e.g. é, ł, ñ, ö, ø, š), other foreign letters (e.g. ß;  ð;  α, β, Δ), sophisticated punctuation (e.g. —, †), and mathematical symbols (e.g. →, ∞, ½, ×, ∑, ∏, ±, º, ²).  

The automated options (the latter two main bullet points) can indeed be a time-saver if used carefully, with rigorous supervision to amend any errors that arise.  

Besides content errors, the authors should also be alert to avoid stylistic or formatting clashes.  For example, various databases might specify the date using differing formats (27 Jul. 2024 versus 27/06/2024 versus July 27, 2024 versus 06/27/2024 versus 2024-07-27).  These should all be harmonised to a consistent format in the authors' own database.  

 

Citations in text

The two most common ways of citing references within the text of a academic paper are with the numerical enumerator or with author & year.  When a numerical enumerator is used, it may or may not be superscripted.  

Enumeration

References can be enumerated either in the order in which they are cited, or by arranging the reference list in some logical sequence — most commonly by alphabetical arrangement of the respective first authors' surnames, although some other arrangement, such as chronological order, could be apt in specific circumstances.  

In modern academic papers Indian numbers (1, 2, 3, ...) are almost always used for the enumeration.  In principle, roman numerals (i, ii, iii, iv, ... or I, II, III, IV, ...),  letters (a, b, c, ... or A, B, C, ...) or symbols (*, †, ‡, ...) could be used;  however they are seldom used by academic publishers nowadays, mainly due to their impracticality when dealing with dozens or potentially hundreds of references.  

Superscripted numbers

When using superscripted numbers there is no need for a space between the preceding word and the citation. A range should ideally be indicated with an en-dash.  Citations can come before or after punctuation (stylistic choice).  

There is no change in the citation when the author(s) and/or year are explicitly mentioned in the text;  the citation must appear beside the author(s) if the work has been directly referred to, but not if the work mentioned was merely cited within your reference(s).  There is limited scope for elaboration.  When mentioning reference numbers explicitly in the text, no formatting or styling should be used.  Brackets or parentheses are optional (stylistic choice);  if used, they should also be superscripted:  as in (12) or [12].  

CORRECT (with references numbered in order of citation):  
In 1754 Adamson conducted the first classic experiment into gewgaws, but sadly the original publications were destroyed1:307ff.. Research in this field was  recently extended to whatchamacallits2,3 and thingamajigs1:493,4–8. The application getting most attention lately is gizmose.g. 9–11, which Wu et al.10:421 call the "next Big Thing".  However, the developments made in references 3, 4 and 7 are much more relevant to real-world usage of thingamabobs, as elaborated herein, and consistent with the work of Deng and coworkers12 in this area.  

INCORRECT:  
In 1754 Adamson(1: page 307 and following pages) conducted the first classic experiment into gewgaws, but sadly the original publications were destroyed. Research in this field was  recently extended to whatchamacallits2-3 and thingamajigs1,4-8. The application getting most attention lately is gizmossome outstanding examples include 9-11, which Wu [10: page 421] calls the "next Big Thing".  However, the developments made in references 3, 4 and 7 are much more relevant to real-world usage of thingamabobs, as elaborated herein, consistent with the work of Deng in this area12.  

Consistency must be maintained in any stylistic choices!  

Inline numbers

When using inline numbers, brackets or parentheses are mandatory, and there must be a space between the preceding word and the citation.  A range should ideally be indicated with an en-dash.  Citations come before punctuation.  

There is no change in the citation when the author(s) and/or year are explicitly mentioned in the text;  the citation must appear beside the author(s) if the work has been directly referred to, but not if the work mentioned was merely cited within your reference(s).  There is scope for elaboration.  When mentioning reference numbers explicitly in the text, no formatting or styling should be used.  

CORRECT (with references numbered in order of citation):  
In 1754 Adamson conducted the first classic experiment into gewgaws, but sadly the original publications were destroyed [1:307ff.]. Research in this field was  recently extended to whatchamacallits [2,3] and thingamajigs [1:493,4–8]. The application getting most attention lately is gizmos [e.g. 9–11], which Wu et al. [10:421] call the "next Big Thing".  However, the developments made in references 3, 4 and 7 are much more relevant to real-world usage of thingamabobs, as elaborated herein, and consistent with the work of Deng and coworkers [12] in this area.  

CORRECT (with references numbered alphabetically by surname):  
In 1754 Adamson conducted the first classic experiment into gewgaws, but sadly the original publications were destroyed (12, pp. 307ff.). Research in this field was  recently extended to whatchamacallits (1; 2) and thingamajigs (especially 4, 5, & 8–10, cf. 12, p. 493). The application getting most attention lately is gizmos (e.g. 6,7,11), which Wu et al. (7, p. 421) call the "next Big Thing".  However, the developments made in references 2, 8 and 10 are much more relevant to real-world usage of thingamabobs, as elaborated herein, and consistent with the work of Deng and coworkers (3) in this area.  

INCORRECT:  
In 1754 Adamson [1: pages 307ff.] conducted the first classic experiment into gewgaws, but sadly the original publications were destroyed. Research in this field was  recently extended to whatchamacallits [2-3] and thingamajigs[1, pages 493,4-8]. The application getting most attention lately is gizmos [some outstanding examples include 9-11], which Wu[10: page 421] calls the "next Big Thing".  However, the developments made in references [3], [4] and[7] are much more relevant to real-world usage of thingamabobs, as elaborated herein, consistent with the work of Deng in this area [12].  

Consistency must be maintained in any stylistic choices!   

Author & year

Citation by author & year includes the surname of the first-listed author (generally disregarding any subsequent co-first authors) and the identifying year.  In cases of ambiguity, typically a lowercase letter is appended to the year to create unique identifiers.  For a journal article the year indicated was traditionally the year printed on the cover of the journal issue in which the article was printed (which could be different from the copyright year).  With the rise of online journals, the year of "first publication" online is now sometimes used.  Although commonly called "author–date" citation, generally only the years are specified in the citations (the full dates can optionally be specified in the reference list).  

When citing by author & year inline, brackets or parentheses are mandatory, and there must be a space between the preceding word and the citation.  Citations come before punctuation.  Ranges arise less commonly, but if they do an en-dash should be used.  

If the author(s) whose work has been directly referred to are explicitly mentioned in the text, then the citation will include only the year, and must appear beside the author(s); but if the work mentioned was merely cited within your reference(s), then there is no change in the citation.  There is scope for elaboration.  There is no scope to mention reference numbers explicitly in the text.  

Within a group of citations, the arrangement can be alphabetical, or chronological.  

 

CORRECT (with brackets):  
In 1754 Adamson conducted the first classic experiment into gewgaws, but sadly the original publications were destroyed [Zalman, 1950: 307ff.]. Research in this field was  recently extended to whatchamacallits [Bjørnsen & Björnsson, 1999; Beethoven & Mozart, 2005] and thingamajigs [Zalman, 1950: 493; Sinues de Marco et al., 2011;  Janse van Rensburg et al., 2008;  van der Waals & Appleby, 2020;  Wu et al., 2024a;  Franco y Martínez-Bordiú et al., 2016]. The application getting most attention lately is gizmos [e.g. al-Khalili & Papadopoulos, 2022;  Wu et al., 2024b;  de Miguel Jiménez & Anu, 2014], which Wu et al. [2024b: 421] call the "next Big Thing".  However, the developments made by Bjørnsen & Björnsson [1999], Sinues de Marco et al. [2011] and Wu et al. [2024a] are much more relevant to real-world usage of thingamabobs, as elaborated herein, and consistent with the work of Deng and coworkers [2015] in this area.  

CORRECT (with parentheses):  
In 1754 Adamson conducted the first classic experiment into gewgaws, but sadly the original publications were destroyed (Zalman, 1950, pp. 307ff.). Research in this field was  recently extended to whatchamacallits (Bjørnsen & Björnsson, 1999; Beethoven & Mozart, 2005) and thingamajigs (especially Sinues de Marco et al., 2011;  Janse van Rensburg et al., 2008;   van der Waals & Appleby, 2020;  Wu et al., 2024a;  and Franco y Martínez-Bordiú et al., 2016;  cf. Zalman, 1950: p. 493). The application getting most attention lately is gizmos (e.g. al-Khalili & Papadopoulos, 2022;  Wu et al., 2024b;  de Miguel Jiménez & Anu, 2014), which Wu et al. (2024b, p. 421) call the "next Big Thing".  However, the developments made by Bjørnsen & Björnsson (1999), Sinues de Marco et al. (2011) and Wu et al. (2024a) are much more relevant to real-world usage of thingamabobs, as elaborated herein, and consistent with the work of Deng and coworkers (2015) in this area.  

INCORRECT:  
In 1754 Adamson[Zalman, 1950, pages 307ff.] conducted the first classic experiment into gewgaws, but sadly the original publications were destroyed. Research in this field was  recently extended to whatchamacallits[van Beethoven & Mozart, 2005 and Bjørnsen and Björnsson (1999)] and thingamajigs [Zalman1950:pages 493,Marco2011.Rensburg(2008), Waals, Appleby, 2020, Wu 2024.  Franco y Martínez-Bordiú and co-authors, 2016]. The application getting most attention lately is gizmos [some outstanding examples include James & Georgios (2022), Wu 2024. de Miguel Jiménez et al., 2014], which Wu [page 421: 2024] calls the "next Big Thing".  However, the developments made in (Bjørnsen et al.), Sinues etal2011, and [Wu et al., 2024a] are much more relevant to real-world usage of thingamabobs, as elaborated herein, consistent with the work of Deng in this area [2015].  

Prevalence of various citation styles

The following statistics* are indicative of the prevalence of the various citation styles mentioned above.  

  • Numbered in order of citation appearance:  64%
    • Of those, 55% used superscripts, 33% used brackets, and 12% used parentheses. 
  • Author(s) & year:  22%
    • Of those, 100% used parentheses. 
  • Numbered alphabetically by author surname:  9%
    • Of those, 43% used superscripts, 29% used brackets, and 29% used parentheses. 
  • Footnoted in order of citation:  5%
    • Of those, 50% used symbols, and 50% used numbers.  

For citations formatted as subscripts:  

  • Superscripted number (or symbol) after full stop:  88%
  • Superscripted number (or symbol) before full stop:  12%

* These statistics were compiled by Division One Academic and Language Services in 2025 based on a survey of 77 articles in 63 journals.  The articles were mostly from recent decades, from a wide variety of publishers;  the largest number were from the medical field, but with representation of the engineering, chemistry, physics, biology, mathematics and statistics fields too, alongside interdisciplinary publications.  

  

List of references

Basic requirements of reference lists are that they should be

  • accurate;  
  • complete, but without duplication or unnecessary details;  
  • arranged in a sensible order;  and
  • consistently presented in an appropriate style.  

As mentioned above, the two most common ways in which reference lists are ordered is according to the sequence of citations in the text, or alphabetically by the surname of the first author.  Other possibilities include chronological order, or grouping by theme.  

References arranged in order of citation

 CORRECT (in full):  

  1. Zalman, Egon F. J. (1950) A Complete History of Gewgaws, Volume 2;  Springer, Berlin.  
  2. van Beethoven, Heinz & Waltraud A. Mozart (2005) "Why not whatchamacallits?  Manufacture and use in the new millennium", International Journal of Useful Items, 30(7):  A-41–A-49.  
  3. Bjørnsen, Jørgen & Auður Björnsson (1999) "Optimisation of whatchamacallit functionality using CAD, CAM and CFD", International Journal of Useful Items, 24(5):  2051–2059.  
  4. Sinues de Marco, María del Pilar & Daniela Nguyen (2011), "Thingamajig technology — a review based on first principles", Annals of New Technology, 135(S5):  e01350000829.  
  5. Janse van Rensburg, Anna F., Julian P. Alaphilippe & Katarzyna J. Niewiadoma (2008), "Thingamajig efficiency boosted by nanoroughness", Annals of New Technology, 129(7):  e01290000318.  
  6. van der Waals, Johannes D. & Humphrey Appleby (2020), "Recycling of thingamajigs with the aid of a novel resin.  Part A:  manufacture", Green Tech is Good Tech, 5:  2020000500017.  
  7. Wu, Christina Chun-Xia, Xiaoling Lau & Xin Ying Lau (2024a), "Potential effects of worldwide use of thingamajigs on global warming reduction", Green Tech is Good Tech, 9:  2024000500069.  
  8. Franco y Martínez-Bordiú, Francisco de Asís & Geoffrey G. Yunupingu (2016), "Phase transition of thingamajigs at four different pressures in an acidic environment", Southern Hemispherical Engineering Sciences, CXX(viii):  2589–2595.  
  9. al-Khalili, James & Georgios Papadopoulos (2022), "Investigation into the relationship between gizmo size and capacity", International Journal of Useful Items, 47(1):  247–250.  
  10. Wu, Christina Chun-Xia & Sílvia de Melo Falcão (2024b), Modern Gizmo Handbook for Technicians and Professionals;  Prentice-Hall, Washington. 
  11. de Miguel Jiménez, Pedro & Jessica Anu (2014), "Destruction testing of gizmos to improve durability", Southern Hemispherical Engineering Sciences, CXVI(xxi):  5182–5190.  
  12. Deng, Rui, Patrice Gonzales & Enid A. Anderson (2015), "A comparison of gadgets to employ in thingamabob applications", Southern Hemispherical Engineering Sciences, CXVIII(ix):  3813–3817.  

 

References arranged in alphabetical order by surname

The following can also be used without enumeration for author–year citations.  

CORRECT (in full):  

  1. van Beethoven, Heinz & Waltraud A. Mozart (2005) "Why not whatchamacallits?  Manufacture and use in the new millennium", International Journal of Useful Items, 30(7):  A-41–A-49.  
  2. Bjørnsen, Jørgen & Auður Björnsson (1999) "Optimisation of whatchamacallit functionality using CAD, CAM and CFD", International Journal of Useful Items, 24(5):  2051–2059.  
  3. Deng, Rui, Patrice Gonzales & Enid A. Anderson (2015), "A comparison of gadgets to employ in thingamabob applications", Southern Hemispherical Engineering Sciences, CXVIII(ix):  3813–3817.  
  4. Franco y Martínez-Bordiú, Francisco de Asís & Geoffrey G. Yunupingu (2016), "Phase transition of thingamajigs at four different pressures in an acidic environment", Southern Hemispherical Engineering Sciences, CXX(viii):  2589–2595.  
  5. Janse van Rensburg, Anna F., Julian P. Alaphilippe & Katarzyna J. Niewiadoma (2008), "Thingamajig efficiency boosted by nanoroughness", Annals of New Technology, 129(7):  e01290000318.  
  6. al-Khalili, James & Georgios Papadopoulos (2022), "Investigation into the relationship between gizmo size and capacity", International Journal of Useful Items, 47(1):  247–250.  
  7. de Miguel Jiménez, Pedro & Jessica Anu (2014), "Destruction testing of gizmos to improve durability", Southern Hemispherical Engineering Sciences, CXVI(xxi):  5182–5190.  
  8. Sinues de Marco, María del Pilar & Daniela Nguyen (2011), "Thingamajig technology — a review based on first principles", Annals of New Technology, 135(S5):  e01350000829.  
  9. van der Waals, Johannes D. & Humphrey Appleby (2020), "Recycling of thingamajigs with the aid of a novel resin.  Part A:  manufacture", Green Tech is Good Tech, 5:  2020000500017. 
  10. Wu, Christina Chun-Xia, Xiaoling Lau & Xin Ying Lau (2024a), "Potential effects of worldwide use of thingamajigs on global warming reduction", Green Tech is Good Tech, 9:  2024000500069.  
  11. Wu, Christina Chun-Xia & Sílvia de Melo Falcão (2024b), Modern Gizmo Handbook for Technicians and Professionals;  Prentice-Hall, Washington. 
  12. Zalman, Egon F. J. (1950) A Complete History of Gewgaws, Volume 2;  Springer, Berlin.  

Determining which part of a printed name is the surname (family name) can be difficult. Often online databases classify the names correctly — but not always.  

Notice that particles ("van", "van der", "de", etc.) are often ignored in alphabetising surnames — but not always.  There are conventions in various countries, although individual names may occasionally deviate from those conventions.  Fundamentally the particles are more associated with the surname (family name) than the given names (personal names), so they are often included when the reference is cited or the author is mentioned.  The entire surname (with particle) is kept together for each primary author in the above list (a recommended style).  Just to aid interpretation, the portion of the surname used for alphabetising is rendered in bold:  that would not be necessary in general (although such contrast can be helpful for readers skimming a list).  

Nowadays it is expected that accents (or other embellishments) on letters are retained, but typically they do not affect the sequencing of names.  Thus, in non-specialist publications, names spelled with "ø" or "ö" will be ordered as if they were spelled with "o".  

Spacing of year, volume number, issue number, and page(s)

An unfortunate habit persists in some journals, particularly in the medical field, of presenting the year, volume number, (optionally) issue number, and page(s) without any spaces.  For example, "2009;64(4):614-619."  This ugly style has practically no justification in the modern times;  one imagines that such styles were introduced in the pre-internet era, when articles were printed on paper and the potential cost saving of using (say) 0.1% less paper might have been considered by the publisher to be outweigh the inconvenience to readers from the reduced legibility.  

Wherever possible it is recommended to include spaces as in either "2009; 64(4): 614–619", or "2009; 64 (4): 614–619."  Examples of journals that follow this style (from a variety of publishers, in a variety of fields) include Analytical Chemistry, Langmuir, Proc. Inst. Mechanical Engineers Part H — J. Eng. in Medicine, Soft Matter, The Lancet, and The Medical J. Australia.  

At the other extreme, a small number of publications (e.g., Proc. IEEE, and The Scientific World J.) use an even further expanded style that explicitly labels the volume number, issue number, and page range.  For example,  "vol. 51, no. 1, pp. 140–147, Feb. 2004."

Prevalence of various reference styles

The following statistics* are indicative of the prevalence of the various reference styles mentioned above.  

Citation method:

  • Numbered in order of citation appearance:  64%
  • Author(s) & year:  22%
  • Numbered alphabetically by author surname:  9%
  • Footnoted in order of citation:  5%

Author names:  

  • Without small capital letters:  94%
  • With small capital letters:  6%

Position of year:  

  • Before volume:  44%
  • After authors:  30%
  • Last:  19%
  • Before pages:  6%

Full stop:  

  • Present at the end of the reference:  91%
  • Absent at the end of the reference:  9%

Page range:  

  • Full range (e.g., "2781–2785"):  73%
  • First page only (e.g., "2781"):  17%
  • Condensed range (e.g., "2781–5"):  10%

Punctuation in page range:  

  • En-dash ("–") in page range:  80%
  • Hyphen ("-") in page range:  20%

 

* These statistics were compiled by Division One Academic and Language Services in 2025 based on a survey of 77 articles in 63 journals.  The articles were mostly from recent decades, from a wide variety of publishers;  the largest number were from the medical field, but with representation of the engineering, chemistry, physics, biology, mathematics and statistics fields too, alongside interdisciplinary publications.