[5] In 1968 Billie Jean King became the first woman of the Open Era to sign a pro contract to tour, in a group with Rosie Casals, Françoise Dürr and Ann Haydon-Jones as the women's section of the National Tennis League.
George envisaged us playing a lot of matches and tournaments amongst ourselves and did not expect us to be as much involved in open tennis as later proved to be the case....We joined the six men that he already controlled - Emerson, Laver, Gimeno, Gonzales, Rosewall and Stolle.
In 1970 the National Tennis League (NTL), which employed Rod Laver, Ken Rosewall, Andrés Gimeno, Pancho Gonzales, Roy Emerson and Fred Stolle, prevented its players from entering the tournament because the guarantees were insufficient.
[11] Both professional organizations, the NTL and WCT, banned their contracted players from contesting the grand slams at some stage during their short tenure and this made the International Lawn Tennis Federation, the predecessor of the current ITF, very nervous.
Some of the players he signed to contracts were: Rod Laver, Ken Rosewall, Roy Emerson, Pancho Gonzales, Fred Stolle, Billie Jean King and Rosie Casals.