During the last week I've been reading Dirac. I browsed through his Quantum Mechanics and now I'm reading his Lectures on QFT. In both I found the term "contact transformation" and it seems he's the only one to use it because a few people at the faculty have heard about it but they can't give details as they didn't consider it very important. I don't eather because in Lectures on QFT he refers to the normal time evolution in classical mechanics (the canonical transformation generated by the hamiltonian) as being a contact transformation. Does anyone remember or should I just find his book on classical mechanics and see what he means by that and let you know?