A confidential and closely guarded 1988 agreement between the nation’s two electronic legal research giants, West Publishing Co. and Lexis, has suddenly come to light.

The documents, obtained last week by the Connecticut Law Tribune, show that West made a pact with Mead Data Central, the Dayton, Ohio, parent of Lexis, to share West’s vast collection of American case law, and West’s system for citing it. For that license, Lexis agreed to pay West a fee of $3 million per year.