AP (Associated Press) citation style is used by reporters, editors and others as a guide for grammar, punctuation and principles and practices of reporting. It is updated annually by the Associated Press.
Because it is used primarily in journalistic reporting, it does not have a system of in-text citations or bibliography/works cited formatting.
The IEEE (Institute of Electrical and Electronics Engineers) style is used primarily in engineering and is based on the Chicago style (note/bibliography). The style uses footnotes and corresponding numbers for in-text citations.
Footnote example of citation from a journal article:
 W. Rafferty, “Ground antennas in NASA’s deep space telecommunications,” Proc. IEEE vol. 82, pp. 636-640, May 1994.