The World Book encyclopedia. U-V VOLUME 20 - Chicago : World Book, c1984. - 24 v. : ill. (some col.) ; 26 cm. British Isles suppl. (2 v.) numbered as v. 23-24. ISBN: 0716600846 (set) LCCN: 83050030 LC Class. No.: AE5 .W55 1984 / .W55 1984 Dewey Class. No.: 031