TITLE: Do you know any good introductory resource on sequent calculus?
QUESTION [14 upvotes]: I'm looking for a good introductory resource on sequent calculus suitable for someone who has studied natural deduction before. Books and online resources are both OK, as long as each rule of inference and any notational convention is explained. Thanks.

REPLY [2 votes]: I second here the recommendations of Troelstra and Schwichtenberg's Basic Proof Theory for learning sequent calculus because of its exercises; focus on chapter 3 and do the exercises to get a good grip on standard sequent calculi for classical and intuitionistic logic, as well as get some exposure to a few variations (e.g., single-sided calculi).  von Plato and Negri's Structural Proof Theory is also very good, but it is more of a monograph than a textbook (there are no exercises).  In von Plato and Negri you will find detailed and systematic discussion of the relationship between natural deduction and sequent calculi throughout the book, a discussion that is is largely missing from Troelstra and Schwichtenberg (though it must be said that T and S do prove that various sequent calculi are equivalent with natural deduction and with certain Hilbert/Frege-style proof systems).