In January 1976 the Communist Party of Kampuchea  promulgated the "Constitution of Democratic Kampuchea". The Constitution provided for a "Kampuchean People's Representative Assembly"  to be elected by secret ballot in direct general elections and a State Praesidium to be selected and appointed every five years by the KPRA. The KPRA met only once, a three-day session in April 1976. The members of the KPRA, however, were never elected; the Central Committee of the CPK appointed the chairman and other high officials both to it and to the State Praesidium. Plans for elections of members were discussed, but the 250 members of the KPRA were in fact appointed by the upper echelon of CPK. Democratic Kampuchea was an atheist state, but Buddhist influences still persisted.  All religions were banned, and the repression of adherents of Islam, Christianity, and Buddhism was extensive. Nearly 25,000 Buddhist monks were massacred by the regime. In actual fact, all power belonged to the Standing Committee of CPK, the membership of which comprised the Secretary and Prime Minister Pol Pot, his Deputy Secretary Nuon Chea and seven others. It was known also as the "Centre", the "Organisation," or "Angkar" and its daily work was conducted from Office 870 in Phnom Penh. For almost two years after the takeover, the Khmer Rouge continued to refer to itself as simply "Angkar." It was only in a March 1977 speech that Pol Pot revealed the CPK's existence. It was also around that time that it was confirmed that Pol Pot was the same person as Saloth Sar, who had long been cited as the CPK's general secretary.

Based on the above article, answer a question. What all names had the Prime Minister of the CPK gone by?
Pol Pot