sentences:  Unable to afford the asking price, and concerned that, ostensibly because of the former private owner's tax concerns, Witten refused to reveal the provenance of the map, Yale contacted another alumnus, Paul Mellon, who agreed to buy it (for a price later stated to be about $300,000) and donate it to the university if it could be authenticated.Recognizing its potential importance as the earliest map unambiguously showing America, Mellon insisted that its existence be kept secret until a scholarly book had been written about it.Even the three authors of the book were chosen from among the small number of people who had seen the map before Mellon bought it—two British Museum curators and Marston.