" 
 ::::::::Of course, and I would be very interested to see a reliable source that says ISO and gravitational are equivalent, as the article currently does (""save for centrifugal...""). 
 ::::::::""...any gravitational effect is due to reference frame acceleration.""  Very true.  To make sense the statement would need a qualifier similar to the statement currently in the article, and it would have the same problem; stating two things are the same if you ignore their differences. That is why I don't see how the current statement in the article is any better than 2.0 equals 5.0, save for 3.0.  Although it is correct, it gives the wrong impression (that 2 equals 5, or that ISO is equivalent to the gravitational definition).   "