In order to account for different schedule lengths, roster sizes, and scoring environments, Hockey Reference adjusts goals, assists and points. They are adjusted to an 82-game schedule with a maximum roster size of 18 skaters and league averages of 6 goals per game and 1.67 assists per goal. This was the scoring environment in the 1970s.
Hockey Reference provides a nice example using Gordie Howe's career year in 1952-53. You can see the math here.