The abstract must be concise, yet should accurately outline the content of the manuscript (see the Categories of Articles page of each journal for abstract length requirements for each type of article). Because these abstracts are used by secondary services (e.g., MEDLINE, Chemical Abstracts, Web of Science, Scopus), they should recapitulate in abbreviated form the purpose of the study and the experimental technique, results, and data interpretations. Data such as the number of test subjects and controls, strains of animals or viruses, drug dosages and routes of administration, tumor yields and latent periods, length of observation period, and magnitude of activity should be included. Vague, general statements such as "The significance of the results is discussed" or "Some physical properties were studied" should be avoided. Important terms relevant to the content of the manuscript should be incorporated into the abstract to assist indexers and searchers. Abbreviations should be kept to an absolute minimum; however, if they are needed, they must be explained at first mention within the abstract so that it can be understood as an independent unit from the remainder of the manuscript. Do not cite references in the abstract.