On contraction and the modal fragment
Kai Brünnler, Dieter Probst, Thomas Studer · Mathematical logic quarterly · 2008
Abstract We observe that removing contraction from a standard sequent calculus for first‐order predicate logic preserves completeness for the modal fragment. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)