When citing a reference with more than two (or three) authors, it is common to give only the last name of the first author followed by et al., which is an abbreviation of the Latin phrase et alii, meaning “and others”. Note that a period comes after the letters “al”, because this word is an abbreviated form, but not after “et”, because this word is not an abbreviation.

Efforts towards a sustainable strategy have been initiated by the Swedish government (Gerhardt et al., 2013).