i have restored the three see also references are the two thesis references readily available to readers in the u s and u k are there web links if not would it be feasible to put the thesis references online somewhere and then link to them something that i am not clear about is whether a grey box model must always also be a statistical model the first paragraph from statistical model general remarks is relevant here and is copied below a statistical model is a special type of mathematical model what distinguishes a statistical model from other mathematical models is that a statistical model is non deterministic thus in a statistical model specified via mathematical equations some of the variables do not have specific values but instead have probability distributions i e some of the variables are stochastic in the equations of a grey box model is it required that there be stochastic variables i think that the article would benefit from making that clear