The famous VSEPR theory was proposed by first Sidgwick & Powell. It was modified then by Nyholm & Gillespie.
I was reading Inorganic Chemistry by J.D.Lee where he discusses very briefly the theory of Sidgwick & Powell; I couldn't somewhat conceive the language. So, I googled it but to my misfortune I could nowhere get more info other than this:
The idea of a correlation between molecular geometry and number of valence electrons (both shared and unshared) was originally proposed in 1939 by Ryutaro Tsuchida in Japan, and was _independently presented in a Bakerian Lecture in 1940 by Nevil Sidgwick and Herbert Powell of the University of Oxford. In 1957, Ronald Gillespie and Ronald Sydney Nyholm of University College London refined this concept into a more detailed theory, capable of choosing between various alternative geometries 
Everyone would give the historical info that Sidgwick & Powell was the first to introduce the theory which was later modified to the present VSEPR theory. I don't want that!
Can anyone please help me to bring me forward the original Sidgwick-Powell theory? Also the million-euro question: What are the differences between the two theories? In another way to say: What were the modifications that Mr. Nyholm & Gillespie brought forward that "improved the original" theory?