400. That’s an error.

Google cannot redirect you to http://www.abebooks.it/servlet/SearchResults?tn=C.+Plini+Secundi+Naturalis+historiae+libri+xxxvii.,+recens.+et+comm.+criticis+instruxit+I.+Sillig because the request was invalid.

This might be because the link was created a long time ago. Try your search again on Google. That’s all we know.