The Verify digit is base eleven, and will be an integer concerning 0 and 9, or an 'X'. The program for thirteen-digit ISBNs isn't compatible with SBNs and may, generally speaking, give another Test digit from the corresponding 10-digit ISBN, so will not supply the same security towards transposition. https://directorylinks2u.com/listings13306747/gr%C3%BAas-con-operador-en-sevilla-an-overview