1. Amazon link: https://www.amazon.com/Introduction...=sr_1_1?s=books&ie=UTF8&qid=1499644981&sr=1-1 ISBN: 978-0131118928 This is the book that my class syllabus suggests based off ISBN number, however it is $119.00 to buy off Amazon. 2. Amazon Link: https://www.amazon.com/Introduction...-1&keywords=Introduction+to+Quantum+Mechanics ISBN: 978-1107179868 This book seems to be the same, second edition and all, but has a DIFFERENT ISBN and is only $66.64. What is the difference, is there any difference, in these two links? Thank you.