Conversation so far:
What is the name of Karlheinz Stockhausen's wife ?
Doris Andreae.
When was he married to Doris Andreae ?
On 29 December 1951.
How many children did they have together ?
Together they had four children.
Did he have any other wives ?
he married Mary Bauermeister.

Question: When did he marry Mary Bauermeister ?
Self-contained rewrite: When did Stockhausen marry Mary Bauermeister ?