Over time we have accumulated what has been benefitial for us and for several of our clients.
Incase this may help you, we have created links to these books and products, several of which we have an affiliate relationship with. If you have any questions about that, please do ask.
I have researched and like the products I have linked here. Please use your judgement when buying any of them. If anything feels or looks bad - DONT get it. My hope is that I have found some valuable items but in case this is not for you, you can use these as spring board for finding what you need.