In the Harvard system the basic pattern for a journal article reference is:
Author surname, initials. (Year) Title of article. Journal name. Volume number (Issue or part number), first and last page numbers.
Here's an example reference:
Feldman, H.N. (1993) Maternal care and differences in the use of nests in the domestic cat. Animal behaviour. 45 (1), 13-23.
Mistakes that are commonly made in journal article references include: