The aim of the this paper is to show how the CSL standard defines styles for automatic formation of bibliographic references by modifying an already existing style. Bibliography is an activity that records its development from the first attempts of storing information about books. Different social and external influences have played a role in the development of bibliography as an activity, especially today when technology is of great importance in different areas and thus in automating the formation of bibliographic references. Developing reference management software is extremely important when it comes to scientific papers. Bibliographic data are now available in a variety of formats, so creating a bibliography can be a long process. With newly developed software, managing bibliographic data, creating a bibliography and managing used literature becomes easier and faster. The mentioned software uses the CSL standard to define different styles of bibliographic citations. It is this standard that is the main topic of this paper. In the practical part of the paper, a style modification using the CSL Editor will be shown. Also, in addition to a detailed presentation of the structure of CSL language and the advantages of reference management softare, it will show how important software like Zotero and Mendeley are for different groups such as scientists, professors, students, librarians, but also for developers who continue to improve and work on the most efficient automatic formation of bibliographic citations.