(S (S (NP (BASENP (PRPD Their) (NN opinion)) (PP (IN of) (BASENP (DT the) (NNS changes)))) (VP (VBZ were) (SBAR (IN that) (S (BASENP (DT the) (NN library) (NN operation)) (VP (VBD had) (VP (VBN been) (VP (ADVP (RB considerably)) (VP (VBN tightened) (PRT (RP up)))))))))) (PERIOD .))