S7E7: The One with Ross's Library Book

Rachel and Phoebe befriend a girl Joey's dating and they try to convince him to get more serious with her, however he's reluctant to do so. At least at first. Meanwhile, Ross discovers that his doctoral dissertation is hosted at university's library and is very excited about the fact. Unfortunately, he soon finds out that students aren't exactly reading it, but rather engaging in other 'physical activities' in the paleontology section. Also, Monica runs into Janice and before she knows it, Janice has invited herself to Monica's wedding. Needless to say that neither she nor Chandler are exactly ecstatic about it and they both try to find a way to tactfully uninvite her.