Prof. Mark Liberman (Language Log) points to an article abstract that, after editing, contained the following:

The focus [of this chapter] is [partly] on … generalizations about which members of a set of posited phonological constituents are irreducibly basic and that are derived ….

(The author assures Prof. Liberman that the original was correct, and that the “that” was introduced by a copy editor.) If you’re interested in the which/that debate generally — as opposed to just this instance, in which “which” is indubitably correct and “that” is indubitably not — check out this Chronicle of Higher Education post by Language Logger Geoffrey Pullum; an excerpt:

“Yesterday, December 7, 1941 — a date which will live in infamy — the United States of America was suddenly and deliberately attacked by naval and air forces of the Empire of Japan.” That was how President Franklin D. Roosevelt opened his famous infamy speech, 71 years ago. Ignoring the writing handbooks, he opened with a passive construction, which of course is just right for the rhetorical context (America as innocent victim). And he also ignored another bogeyman rule: He introduced a restrictive relative clause with which.

The false belief that restrictive which is an error stems from a quixotic reform effort of the early 20th century. That attempt to change English failed, but American teachers and editors took note of it, and misinterpreted it as legislation, blithely ignoring the evidence of FDR’s sentence and thousands of others in all kinds of literature.

There’s also this long list of Language Log posts on the subject, with links, for those who are really interested.