 In 1961, Gorbachev pursued a second degree, on agricultural production; he took a correspondence course from the local Stavropol Agricultural Institute, receiving his diploma in 1967.His wife had also pursued a second degree, attaining a PhD in sociology in 1967 from the Moscow Pedagogical Institute; while in Stavropol she too joined the Communist Party.Stalin was ultimately succeeded as Soviet leader by Nikita Khrushchev, who denounced Stalin and his cult of personality in a speech given in February 1956, after which he launched a de-Stalinization process throughout Soviet society.