There are many different ways to cite research sources. This method - parenthetical citation - is currently most in favor.
Start with nothing in your bibliography, and build it based on your parenthetical citations. This will ensure that you haven't listed any sources you didn't cite, and that you haven't cited any sources you didn't list.
Put the last name of the author and the year of publication in parentheses after the relevant piece of text, as in: "Crime dropped 10% between 1995 and 1999 (Croft, 1999)." The comma is optional.
Add the page number(s), if necessary, after a colon, as in: "(Offerman, 1968: 33)."
Check your bibliography to make sure the source is listed in it.
Distinguish between sources written in the same year by the same author; add lower-case letters in chronological order. Thus "(O'Leary, 1993a)" is earlier than "(O'Leary, 1993b)."
Consult a style guide, such as the MLA (Modern Language Association) manual of style, for further details.