clarified NEWS: document_files are officially required since Isabelle2014, but the absence was tolerated as legacy feature;
@string{LNCS="Lect.\ Notes in Comp.\ Sci."}
@string{MIT="MIT Press"}
@string{Springer="Springer-Verlag"}
@book{Nielson,author={Hanne Riis Nielson and Flemming Nielson},
title={Semantics with Applications},publisher={Wiley},year=1992}
@book{Winskel,author={Glynn Winskel},
title={The Formal Semantics of Programming Languages},publisher=MIT,year=1993}
@inproceedings{Nipkow,author={Tobias Nipkow},
title={Winskel is (almost) Right: Towards a Mechanized Semantics Textbook},
booktitle=
{Foundations of Software Technology and Theoretical Computer Science},
editor={V. Chandru and V. Vinay},
publisher=Springer,series=LNCS,volume=1180,year=1996,pages={180--192}}
@book{ConcreteSemantics,author={Tobias Nipkow and Gerwin Klein},
title={Concrete Semantics. A Proof Assistant Approach},publisher=Springer,
note={To appear}}