R&A and USGA to review use of green-reading equipment in golf
Golf's governing bodies are reviewing the use of green-reading devices.
The R&A and United States Golf Association said in a joint statement that they are "concerned" about the development of the equipment.
Its use by players is already limited, but the sport's rule-makers have said they will "address the matter further in the coming months".
"Success should depend on the judgement, skills and abilities of the player," the statement read.
"We are reviewing the use of these materials to assess whether any actions need to be taken to protect this important part of the game."
England's Ian Poulter, who previously criticised the use of greens books, said the review was "common sense".
The two governing bodies announced a series of proposals in March which were designed to make golf quicker and played under simpler rules.
BBC golf correspondent Iain Carter
There has been a growing trend for players to refer to increasingly detailed maps of putting surfaces. These show green undulations and assist in reading the line of putts.
The question is whether this offers artificial assistance and is truly in the spirit of the game. The use of these maps is also time-consuming and slows the pace of play.
The review by the R&A and USGA suggests green maps will eventually be outlawed, meaning players will have to rely on their own perception of undulations, or that of their caddie.