 However, the National Association of Theater Owners urged the creation of an adults-only category, fearful of possible legal problems in local jurisdictions.The "X" rating was not an MPAA trademark and would not receive the MPAA seal; any producer not submitting a film for MPAA rating could self-apply the "X" rating (or any other symbol or description that was not an MPAA trademark).In 1970, the ages for "R" and "X" were raised from 16 to 17.<ref name="Krämer (2005)"></ref> Also, due to confusion over whether "M"-rated films were suitable for children, "M" was renamed to "GP" (for General audiences, Parental guidance suggested),<ref></ref><ref></ref> and in 1971, the MPAA added the content advisory "Some material not generally suitable for pre-teenagers".<ref></ref> On February 11, 1972,<ref></ref> "GP" was revised to "PG".