I cant make a literature references about 'variable' in my title

[Tavrobel]

and are you sure acceleration due to gravity is a variable?

Assuming that Mister _nuke here does his calculations on multiple planets/heavenly bodies, of course it is! Also, g changes based on where you are, above or below sea level, so it is technically variable, although I've only ever used it as the constant 9.8 m/s^2. Sometimes 10 m/s^2.