CSE (Council of Science Editors) Style is widely used in scientific disciplines, particularly in the natural and physical sciences. The CSE manual describes three systems of documentation. All three systems use a reference list at the end of the paper with complete source information. The Name-Year system uses parenthetical citations consisting of the author's last name and year of publication; the Citation-Sequence and Citation-Name systems both use numbered references in the text to refer to the reference list at the end. In Citation-Sequence, the reference list is presented and numbered in the order the sources appear in the text, while in Citation-Name, the reference list is numbered alphabetically by author's last name.