2008-09-18 wenzelm 2008-09-18 added deriv.ML: Abstract derivations based on raw proof terms.
1999-01-12 wenzelm 1999-01-12 Thm of string * tag list;
1997-02-21 paulson 1997-02-21 Replaced "flat" by the Basis Library function List.concat
1996-09-26 paulson 1996-09-26 Added catch-all clause to drop, preventing exception Match
1996-03-21 paulson 1996-03-21 Changes required by removal of the theory argument of Theorem
1996-03-20 paulson 1996-03-20 New module for proof objects (deriviations)