Of his eight encyclicals, Pope Paul VI is best known for his encyclical Humanae vitae (Of Human Life, subtitled On the Regulation of Birth), published on 25 July 1968. In this encyclical he reaffirmed the Catholic Church's traditional view of marriage and marital relations and a continued condemnation of artificial birth control. There were two Papal committees and numerous independent experts looking into the latest advancement of science and medicine on the question of artificial birth control. which were noted by the Pope in his encyclical The expressed views of Paul VI reflected the teachings of his predecessors, especially Pius XI, Pius XII and John XXIII and never changed, as he repeatedly stated them in the first few years of his Pontificate

Which one of Paul Vi's encyclicals best known in Catholic history?