Sequential History in Herlihy and Wing's Linearizability paper
I've come to the conclusion that the constraint "each response is followed by a matching invocation" should omit the word "matching", and the paper should be read as if it weren't there. My evidence for this is that related literature and conference proceedings seem to omit it, either literally or effectively.

For example, the proceedings Principles of Distributed Systems: 14th International Conference (Google Books) includes a summary of a sequential history and linearizability and omits the second constraint completely:


  History $H$ is called Sequential if the first event of $H$ is an invocation, and each invocation, except possibly the last, is immediately followed by a matching response.


Another conference proceedings that I found, Networked Systems: Second International Conference (Google Books) includes the second constraint without the word "matching":


  A history is sequential if its first event is an invocation, and then (1) each invocation event, except possibly the last, is immediately followed by the matching response event, and (2) each response event, except possibly the last, is immediately followed by an invocation event.