How about the official Star Wars WOOKIEPEDIA? IT DOESN'T GET ANY MORE OFFICIAL THAN THAT YOU INCREDIBLE GIT.
http://starwars.wikia.com/wiki/Yoda
Quote:
When Luke Skywalker, son of Anakin Skywalker, arrived on Dagobah, he briefly encountered Luke. However, he kept his true identity to himself, acting like a primitive lifeform as a means to test Luke, although he did promise to lead Luke to him
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