X rating - Wikipedia

Whatever Happened to the X Rating?

cinema history - Why would a movie that appears pornographic via it's rating (X) receive an Academy Award? - Movies & TV Stack Exchange

A History of the X and NC-17 Ratings – The Hollywood Reporter

X - Rotten Tomatoes

Midnight Cowboy - Wikipedia

Reviewing the NC-17 Film Rating: Clear Guide or an X by a New Name? - The New York Times

Fast X is given a 12A age rating

Fifty Shades of Grey' will heat up your week

Review: 'Fast X” gears up for more road rage, sets up sequels - Brainerd Dispatch

James Bond film Thunderball nearly given 'X' rating by censors