One thing I find frustrating when trying to get a handle on this theorem is the number of different forms presented in the literature. I understand this to be due to it being very general theorem applicable to many different contexts. Not that the world needs a new, slightly different looking definition of RTT, but I have tried to look at it from a 'fluid parcel' (a.k.a. material volume) and 'control volume' point of view. Based on general reading from multiple sources, this is a definition I've come up with which makes sense to me because it's very similar to the idea of the "Material Derivative". But, is it correct? Thank you in advance.