The phrase "drug references" refers to mentioning or talking about drugs, including their effects, use, or presence, in things like songs, movies, or conversations. Full definition
Rated PG - 13 for some sexual content and brief drug references. (sfgate.com)
There's a study out that looks at a number of drug references in music. (relevantmagazine.com)
The film is rated PG - 13 for thematic elements associated with a university campus (i.e., sexual discussions and mild drug references). (christiananswers.net)