Supplementary information can be a very valuable tool in academic publishing, allowing authors to provide important additional material—such as experimental details, data sets, chemical structures, images, tables, audio files, and videos—which are necessary to support the main article but cannot be included in it for various reasons including file format or medium. Supplementary information can also be useful in journals with strict length limitations.
Any supplementary information provided should directly have relevance to the manuscript and should not extend beyond its scope. It is also important that the quality and presentation of the supporting material match that of the main paper. Most publishers do not edit the supplementary information, so it is up to the authors to ensure the clarity of this information upon submission. All files must be original. However, if any of the data is published previously, then the authors need permission to use it and must cite the original source.
Many journals require that references included in the supplementary information are also listed in the main article to guarantee that the original papers are cited properly. This helps in contributing to the citation metrics for those sources.
The number and size of the supporting files should be kept as small as possible. This allows readers to download the files quickly and easily. Most journals accept common formats, such as Adobe Acrobat (.pdf), MS Word (.doc and .docx), MS Excel (.xls, .xlsx), JPG/JPEG images, encapsulated postscripts (.eps), QuickTime movies (.mov), MPEG/MPG animations (.mpg, .mp4, .mp3), audio files (.wav), and others.
Categories of Supplementary Material
There are different types of supplementary material; these include:
- Experimental and computational details, as well as an elaborate description of the methods used;
- Large data sets and raw information;
- Supplementary tables, equations, and figures must be accompanied by a legend. It should have a different numbering system from that used in the main manuscript to avoid confusions. For example, table/equation/figure S1, S2, S3, and so on (instead of table/equation/figure 1, 2, or 3). The figures must be provided in a suitable format and should have a high resolution.
- Supplementary audio and video files should be of good quality, have a reasonable size, and be in an appropriate format. Authors must provide the corresponding legends in a separate document.
Whenever possible, the supplementary information should be combined into a single PDF file. This facilitates access and handling by editors, referees, and readers. This is usually the case for text, tables, figures, and equations. Audio and movie files must be provided separately in a suitable format (after checking the journal guidelines for allowed formats). With these simple guidelines, authors can significantly improve the use of supplementary information to strengthen and enhance their academic publications.