CSE / Science style is usually used in the Sciences. CSE stands for Council of Science Editors.
There are three different types of CSE / Science style. These are citation-sequence; citation-name; and name-year. The names of the style types correspond to their organization. The version you use will depend on your assignment, class, professor's preference, or publication need.
In citation-sequence, references should be indicated by a number that corresponds to the number of the reference in the bibliography. The in-text citation "1" directs the reader to the first reference in the reference list.
In citation-name, references are listed alphabetically in the reference list, but then referred to by number in the text. [Example: Gopher snakes can be found in a variety of habitats (68); and will hunt frogs on occasion (14).]
See example in article. Look for the numbers in the introduction. They do not start at one and move sequentially.
In name-year, use author last name and date of publication in in-text citations. [Example: Some studies have shown that dogs experience love (Weingarten and Pierce 2007).] Items in the reference list should be listed alphabetically.