You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "when was the first heart transplant performed in the world?" whose answer is December 3, 1967.
Each document should contain about 30 words, and these documents should contain useful information.

Query: when was the first heart transplant performed
Useful Output:

Doc 1: The first heart transplant in a human occurred on December 3rd, 1967. The six-hour surgery was performed by South African Christiaan Barnard
Doc 2:  performed in South Africa by Dr. Christiaan Barnard on Dec. 3, 1967 — actually worked. They were able to successfully transplant a heart
Doc 3: The first heart transplant was attempted in 1905 with two canines. The heart was transplanted immediately from the smaller donor dog into the neck of the
Doc 4: Decades of clinical and animal-based research laid the foundation for the first heart transplant performed on December 3, 1967 by Christiaan Barnard in Cape
Doc 5: Just before 6 a.m. on Sunday 3 December 1967 a new heart in the chest of Dr Louis Washkansky was electrically shocked into action. The first human heart