"A revenue ruling is an official interpretation by the IRS of the Internal Revenue Code, related statutes, tax treaties and regulations. It is the conclusion of the IRS on how the law is applied to a specific set of facts." (IRS Website)
"Revenue rulings are published in the Internal Revenue Bulletin . . . " (IRS Website)
The following citation resources may be informative.
Below are links to select sources offering revenue rulings.
Below is a pertinent abbreviation.