Science can be thought of as the process of adding to the vast body of knowledge. Therefore, an essential part of scientific writing involves referring to studies published before yours. There are various ways of referring to your colleagues’ work, some of which are better than others. Here, we outline some tips to help you refer to the work of your colleagues elegantly and appropriately.
By definition, studies published before yours are “previous studies.” Unfortunately, there is a tendency in modern scientific writing to overuse the word “previous.” Many of these uses are unnecessary because the previous nature of the study is implied.
Previous studies have reported overall survival rates of 10–20% [1,2].
Studies have reported overall survival rates of 10–20% [1,2].
Note that omitting the word “previous” does not weaken the meaning of the sentence. Note also that in-text citations are presented after the statements regarding previous studies. It is important to pay attention to the number of the noun “study/studies.” If you cite only one study, then you must not use the plural “studies.”
Incorrect: Previous studies reported an overall survival rate of 10% .
Correct: A previous study reported an overall survival rate of 10% .
Nevertheless, there are situations in which it is appropriate to use the word “previous.” In a paragraph, if you are referring to the present work as well as to other studies, it is often appropriate to distinguish those studies from yours to avoid confusion on the part of the reader.
In the present study, we found an overall survival rate of 10%. In previous studies, overall survival rates of 10–20% have been reported [1,2].
Avoid using apostrophe + s, particularly after et al.
Another tendency in modern scientific writing is to use the possessive form “apostrophe + s,” even after the abbreviation et al. This construction looks awkward in print, and sounds even more awkward when read aloud, as demonstrated in the following example.
In Boney et al.’s study, prolactin levels were found to correlate with the severity of illness.
This sentence would be much easier to read if it were reconstructed as follows:
Boney et al. found that prolactin levels correlated with the severity of illness.
Notice also that the sentence is much more elegant and readable in the active voice as opposed to the passive voice in the first example.
Cite your colleagues’ work early, but not too early
When you mention work by other authors, it is important to place an in-text citation at the end of the first sentence, even if more than one complete sentence is required to describe the work. This way, you cannot be accused of making statements without attribution.
Boney et al. performed a study of 250 peri-menopausal women . They measured prolactin levels daily for one month and compared the values with those of pre- and post-menopausal women.
Note that both sentences refer to the work of Boney et al. and that the in-text citation is placed after the first sentence. Note also that the citation could have been placed earlier in the sentence; however, doing so would be awkward and might make it more difficult for the reader, as in the example below.
Boney et al.  performed a study of 250 peri-menopausal women. They measured prolactin levels daily for one month and compared the values with those of pre- and post-menopausal women.
Correct use of the abbreviation et al.
The abbreviation et al. represents the Latin phrase et alia, which means “and others.” An example is “Boney et al.” Because there are several ways to cite works using “et al.,” we recommend consulting the authors’ instructions of your target journal. One rule that must always be followed is that the “et” is a complete word and never takes a dot after it. The word “alia” sometimes takes a dot and sometimes does not. Please consult the target journal for guidance. Some target journals ask the author to italicize the abbreviation “et al.” because it is a Latin phrase. If the instructions to the authors do not provide guidance as to italics, reading sample articles online may help.
Never mind about the year
Finally, some scientific writers tend to mention the publication year of a colleague’s work when doing so is not necessary because of the in-text citation. Writers should mention the year only when doing so is necessary in the context of the argument the author is building.
No diagnostic modalities were available until the development of the Boney-Maroney procedure in 1962 .
Most of the time, however, an interested reader can determine the year of a study by consulting the reference list.
This was by no means an exhaustive list of recommendations. Interested readers may consult The Elements of Style by William Strunk and E. B. White for in-depth guidance.