Andrew Loomis books
This is a link to all of Andrew Loomis’s books, which were printed in the 20th century but provide excellent tips on perspective, anatomy, balance, etc… http://alexhays.com/loomis/
Coupla Links for help on perspective for you today!
-It looks like a lot but the pages are small so you can do it! :»
-ConceptArt Link that covers basic perspective. You need to sign in to see it though.
-Perspective tool to reference to when you need it.
Keep Drawing! Good luck!