International Standard Book Number in 1965, has – 340 indicating the publisher, 01381 their serial number, and 8 being the check digit. This can be converted to ; the check digit does not need to be re-calculated. Since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with "Bookland" European Article Number EAN-13s. An ISBN is assigned to each edition and variation (except reprintings) of a book. For example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January
What Lies Below was a "pretty cool" mystery-of-the-week, and "while not quite as strong as when the mythology is in full gear, 'What Lies Below' was nonetheless a compelling hour of television." He was however bothered that there was no further information about the parallel universe. UGO Networks writer Alex Zalben compared "What Lies Below" to the similarly-plotted "The X-Files" episode "Ice". Zalben concluded, "Though both episodes are very good, 'Ice' is one of the best "X-Files" hours ever, perfectly channeling – but not ripping off – John Carpenter's "The Thing"." Director Deran Sarafian submitted "What Lies Below" for consideration in the Outstanding