when was the yellow card introduced in football
Penalty card The idea of using language-neutral coloured cards to communicate a referee's intentions originated in association football, with English referee Ken Aston.[2] Aston had been appointed to the FIFA Referees' Committee and was responsible for all referees at the 1966 FIFA World Cup. In the quarter finals, England met Argentina at Wembley Stadium. After the match, newspaper reports stated that referee Rudolf Kreitlein had cautioned both Bobby and Jack Charlton, as well as sending off Argentinian Antonio Rattin. The referee had not made his decision clear during the game, and England manager Alf Ramsey approached FIFA for post-match clarification. This incident started Aston thinking about ways to make a referee's decisions clearer to both players and spectators. Aston realised that a colour-coding scheme based on the same principle as used on traffic lights (yellow – stop if safe to do so, red – stop) would transcend language barriers and make it clear that a player had been cautioned or expelled.[2] As a result, yellow cards to indicate a caution and red cards to indicate an expulsion were used for the first time in the 1970 FIFA World Cup in Mexico. The use of penalty cards has since been adopted and expanded by several sporting codes, with each sport adapting the idea to its specific set of rules or laws.
National Football League uniform numbers Players in the National Football League wear uniform numbers between 1 and 99, and no two players on a team may wear the same number on the field at the same time. Rules exist which tie a player's number to a specific range of numbers for their primary position. Additionally, rules exist which limit who may handle the ball on offense, generally players who are designated as offensive lineman, who wear numbers 50-79, are not allowed to handle the ball during a play from scrimmage, though they are allowed to do so if they report to the referee as playing out of position.