na INLIS000000000008787 Ind 0010-1118008787 Error detecting decimal codes VERHOEFF, J. Jacobus Verhoeff Amsterdam Mathematisch Centrum 1969 118 p. : ill. ; 25 cm. 118 p. : ill. ; 25 cm. 511.135VERe Bibl.: p. 112-118 511.135 MATHEMATICS 134/71-mfn10566