CARNOUSTIE, Scotland — The U.S. Golf Association and R&A plan to severely restrict the information allowed in green-reading books.

Beginning Jan. 1, 2019, the move will effectively render the books impractical to players who have increasingly leaned on them for reading putts.

Three golf industry rules experts confirmed the plan to Golfweek. The sources spoke on the condition of anonymity because they were not authorized to speak publicly on the move.

“We announced last year that we were reviewing green-reading materials and expect to be able to give a further update in the coming weeks,” an R&A spokesman said. “We believe that the ability to read greens is an integral part of the skill of putting and remain concerned about the rapid development of increasingly detailed materials that players are using to help with reading greens during a round.”

The USGA provided the following statement: “We haven’t made any public announcements on Green Reading Materials since our joint announcement with The R&A last year, but we do plan an update on our review process in the coming weeks. It’s simply too premature to discuss, but we promise to keep everyone informed as we move forward.”

The basis for the action will be skill-based, with the USGA and R&A seeking to protect the art of green reading by eye and not by a book featuring complex charts detailing slope. Pace of play is believed to a factor in the joint decision as players increasingly analyze the contour data both in fairways and on putting surfaces.

Asked about his use of the books following an opening-round 72 at the British Open, Jordan Spieth reacted as if an announcement had already been made.

“I don’t think we’re allowed to use them starting next year, is that right?” he said. “Which I think will be much better for me. I think that’s a skill that I have in green reading that’s advantageous versus the field, and so it will be nice. But while it’s there, certain putts, I certainly was using it and listening to it.”

The rules are expected to address visual and informational elements of the books. New Rules of Golf language will focus on presentation elements to end the current level of detail.

The green readouts, now a weekly part of PGA Tour and European Tour life, cost anywhere from $150 to $300 a week and have also become increasingly popular at the college level. The USGA and R&A, despite their stated concerns about the books, provide the readouts at the U.S. Open and British Open.

The action regarding the books also gives the USGA and R&A an opportunity to make a joint effort at protecting skill without impacting everyday amateur golf while they also examine the role of technology in driving distance increases.