(S (S (BASENP (DT This)) (VP (VBZ is) (ADJP (ADJP (NP (QP (ADVP (RBR more) (IN than)) (NN 3500)) (NNS years)) (JJR earlier)) (SBAR (IN than) (S (VP (ADVP (RB previously)) (VBN known))))))) (PERIOD .))