Your best bet is eBay or one of the rare book sites like ABE (Advanced Book Exchange). Unbelievably, I have a copy that I purchased at a thrift shop for 20 cents years ago (they were overflowing with books and wanted to get rid of them, so sold them for 5 for $1.00). Strange but true category: Originally, Addison Wesley published a separate Solution Key for this book, which they no longer do. (The long answers and proofs are right in the margins in the Teacher's Edition, and a few spilled over into the back into a special section for proofs that did not fit within the text). The student book and separate solution key recently sold for a little over $400 on eBay!