The general rule is to give surnames of authors (no initials) and date of publication. If a publication has two authors, give the surnames of both; if it has more than two, only give the name of the first and replace the names of the others with "et al."
The citation is always included within a sentence. Depending on the context, the authors' names can be part of the sentence with the date in parentheses or the names and date can be in parentheses.
Examples:
The publications by Peltonen et al. (1994) and Apel-Birkhold and Walton (1996) are research papers; that by Walton (1994) is a review.