The check digit is base eleven, and may be an integer amongst 0 and 9, or an 'X'. The process for 13-digit ISBNs is not appropriate with SBNs and can, normally, give a special check digit within the corresponding ten-digit ISBN, so will not provide exactly the same safety https://phase2directory.com/listings13306888/the-basic-principles-of-cami%C3%B3n-gr%C3%BAa-en-alcal%C3%A1-de-guada%C3%ADra