Google for years operated a secret program that used data from past bids in the company’s digital advertising exchange to allegedly give its own ad-buying system an advantage over competitors, according to court documents filed in a Texas antitrust lawsuit.

The program, known as “Project Bernanke,” wasn’t disclosed to publishers who sold ads through Google’s ad-buying systems. It generated hundreds of millions of dollars in revenue for the company annually, the documents show. In its lawsuit, Texas alleges that the project gave Google, a unit of Alphabet Inc., an unfair competitive advantage over rivals.

The documents filed this week were part of Google’s initial response to the Texas-led antitrust lawsuit, which was filed in December and accused the search company of running a digital-ad monopoly that harmed both ad-industry competitors and publishers. This week’s filing, viewed by The Wall Street Journal, wasn’t properly redacted when uploaded to the court’s public docket. A federal judge let Google refile it under seal.

Some of the unredacted contents of the document were earlier disclosed by MLex, an antitrust-focused news outlet.

The document sheds further light on the state’s case against Google, along with the search company’s defense.