Lexis Advance Tax
Lexis Advance Tax is a database on Lexis Advance that is focused on tax law. On the home page for Lexis Advance Tax, you can find the "Tax Overview," which is essentially a treatise about tax law in its entirety. The treatise is searchable and also covers some of the practical considerations for tax planning. The Tax Overview is a great resource to start researching with, and Lexis Advance Tax is a good resource to familiarize yourself with.