George Sutcliffe 040-formal proofsGeorge Sutcliffe 043-formal proofsGeorge Sutcliffe 048-formal proofsGeorge Sutcliffe 059-formal proofsGeorge Sutcliffe 064-casual proofsGeorge Sutcliffe 080-casual proofsGeorge Sutcliffe 085-casual proofsGeorge Sutcliffe 088-casual proofs