Polo taken. The official set of rules and rules interpretations are reviewed and published annually by each country's polo association. Most of the smaller associations follow the rules of the Hurlingham Polo Association, the national governing body of the sport of polo in the United Kingdom, and the United States Polo Association. Outdoor or field polo consists of four to eight 7-minute chukkas, between or during which players change mounts. At the end of each 7 minute chukka, play continues for an additional 30 seconds or until a stoppage in play, whichever comes first. There is a four-minute interval between chukkas
Marco Polo noted that the only Persian source that mentions the princess was not completed until 1310–11, therefore Marco Polo could not have learned the information from any Persian book. According to de Rachewiltz, the concordance of Polo's detailed account of the princess with other independent sources that gave only incomplete information is proof of the veracity of Polo's story and his presence in China. Morgan writes that since much of what "The Book of Marvels" has to say about China is "demonstrably correct" that to claim that Polo did not go to China "creates far more problems than it solves" and