ISO: A Series of Books

I've found that posting here things I'm looking for is a way to find them affordably, sometimes even by bartering. So going with previous successes, I'm searching for the Golden Nature Guide series along with the Golden Science Guides and the Golden Field Guides. I do NOT want new copies, thrift store finds would be swell. It seems our girls are really starting to take a more avid interest in nature and identifying things so a little investment will go a long way. I remember fondly my grandmother's copy of A Golden Guide to Birds or possibly the Golden Field Guide to Birds of North America with notations in her hand about birds she'd seen. I thought I had several of her copies but a search of our bookshelves revealed nothing. So, if anyone has some of these books about and wants to part with them or stumbles across any at a thrift shop, tag sale or whatever...let me know what you'd like in return. Postage+small price for book, a trade...???

In all, there are about 30 of these I'd like to find. The picture is an example of what the covers look like...the newer versions do not catch my eye like these older ones.