The Test digit is foundation eleven, and will be an integer between 0 and 9, or an 'X'. The technique for thirteen-digit ISBNs just isn't suitable with SBNs and will, generally, give another Verify digit within the corresponding 10-digit ISBN, so does not give the same protection against transposition. https://seeyoudirectory.com/listings13309939/gr%C3%BAas-con-operador-en-sevilla-an-overview