This link will take the user to the login screen for Lexis Advance. Once logged in, use the Browse Sources feature and enter the title (Federal Income, Gift and Estate Taxation) in the browse sources box.
WG&L publishes very well regarded tax law treatises and journals. The treatises are often referred to by the names of their authors, e.g. "Bittker & Eustice." The link above takes you to the WG&L database in Westlaw. These materials are also available in Checkpoint.