sentences:  This, however, is no longer the case.In 1983, following the death of Kim Duk-koo from injuries sustained in a 14-round fight against Ray Mancini, the WBC took the unprecedented step of reducing the distance of its world championship bouts, from 15 rounds to 12—a move other organizations soon followed (for boxers' safety).Among those to have been recognized by the WBC as world champions are the undefeated and undisputed champion Terence Crawford, Joe Calzaghe, Floyd Mayweather Jr., Roy Jones Jr., Wilfred Benítez, Wilfredo Gómez, Julio César Chávez, Muhammad Ali, Joe Frazier, Sugar Ray Leonard, Thomas Hearns, Mike Tyson, Salvador Sánchez, Héctor Camacho, Marvin Hagler, Carlos Monzón, Rodrigo Valdez, Roberto Durán, Juan Laporte, Félix Trinidad, Edwin Rosario, Bernard Hopkins, Alexis Argüello, Nigel Benn, Lennox Lewis, Vitali Klitschko, Érik Morales, Miguel Cotto, Manny Pacquiao, Canelo Álvarez, Tony Bellew and Mairis Briedis.