Problem with references in 1st sentence of 4.2.2 #86

The first sentence of Section 4.2.2 has two citations that do not appear in the rendered output:

Description Logics (DLs) were initially introduced as a way to formalise the meaning of frames cite("minsky"); ?> and semantic networks <?php $references->cite("quillian");

should be:

Description Logics (DLs) were initially introduced as a way to formalise the meaning of frames cite("minsky"); ?> and semantic networks cite("quillian"); ?>.