Talk:Vallis (planetary geology)

Bad ISBN
Because it is causing a Checkwiki error #73: "ISBN-13 with wrong checksum", I removed the ISBN:

ISBN 978-0-521-87501-0

An ISBN alone is not a reference; when it's a bad ISBN, it's useless. Knife-in-the-drawer (talk) 14:40, 30 April 2015 (UTC)