<human>: Answer by taking a quote from the following article:

Karlheinz Stockhausen (German: [kaRl'haInts 'StokhaUzn]; 22 August 1928 - 5 December 2007) was a German composer, widely acknowledged by critics as one of the most important (Barrett 1988, 45; Harvey 1975b, 705; Hopkins 1972, 33; Klein 1968, 117) but also controversial (Power 1990, 30) composers of the 20th and early 21st centuries. A critic calls him "one of the great visionaries of 20th-century music" (Hewett 2007). He is known for his groundbreaking work in electronic music, for introducing controlled chance (aleatory techniques or aleatoric musical techniques) into serial composition, and for musical spatialization.

On 29 December 1951, in Hamburg, Stockhausen married Doris Andreae (Kurtz 1992, 45; Maconie 2005, 47). Together they had four children: Suja (b. 1953), Christel (b. 1956), Markus (b. 1957), and Majella (b. 1961) (Kurtz 1992, 90; Tannenbaum 1987, 94). They were divorced in 1965 (Rathert 2013). On 3 April 1967, in San Francisco, he married Mary Bauermeister, with whom he had two children: Julika (b. 22 January 1966) and Simon (b. 1967) (Kurtz 1992, 141, 149; Tannenbaum 1987, 95). They were divorced in 1972 (Rathert 2013; Stockhausen-Stiftung & [2013]).  Four of Stockhausen's children became professional musicians (Kurtz 1992, 202), and he composed some of his works specifically for them. A large number of pieces for the trumpet--from Sirius (1975-77) to the trumpet version of In Freundschaft (1997)--were composed for and premiered by his son Markus (Kurtz 1992, 208; M. Stockhausen 1998, 13-16; Tannenbaum 1987, 61). Markus, at the age of 4 years, had performed the part of The Child in the Cologne premiere of Originale, alternating performances with his sister Christel (Maconie 2005, 220). Klavierstuck XII and Klavierstuck XIII (and their versions as scenes from the operas Donnerstag aus Licht and Samstag aus Licht) were written for his daughter Majella, and were first performed by her at the ages of 16 and 20, respectively (Maconie 2005, 430, 443; Stockhausen Texte, 5:190, 255, 274; Stockhausen Texte, 6:64, 373). The saxophone duet in the second act of Donnerstag aus Licht, and a number of synthesizer parts in the Licht operas, including Klavierstuck XV ("Synthi-Fou") from Dienstag, were composed for his son Simon (Kurtz 1992, 222; Maconie 2005, 480, 489; Stockhausen Texte, 5:186, 529), who also assisted his father in the production of the electronic music from Freitag aus Licht. His daughter Christel is a flautist who performed and gave a course on interpretation of Tierkreis in 1977 (Stockhausen Texte, 5:105), later published as an article (C. Stockhausen 1978).  In 1961, Stockhausen acquired a parcel of land in the vicinity of Kurten, a village east of Cologne, near Bergisch Gladbach in the Bergisches Land. He had a house built there, which was designed to his specifications by the architect Erich Schneider-Wessling, and he resided there from its completion in the autumn of 1965 (Kurtz 1992, 116-17, 137-38). CANNOTANSWER

When did he marry Mary Bauermeister ?
<bot>: On 3 April 1967,