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 song oh christmas tree written?" whose answer is 1824.
Each document should contain about 30 words, and these documents should contain useful information.

Query: when was the song oh christmas tree written
Useful Output:

Doc 1: The first verse of this song appeared in 1820 via August Zarnack's Weisenbuch zu den Volksliedern fur Volkschulehn. Many think he borrowed from
Doc 2: ” - Opening lines to Ernst Anschütz's 1824 version of the German song 'O Tannenbaum' (O Christmas Tree, or 'O Fir Tree'), variations of which go
Doc 3: The carol started life as 'O Tannenbaum' ('O Fir Tree') and the modern version came from the pen of German composer and teacher Ernst Anschütz,
Doc 4: A German Christmas carol, often translated as "O Christmas Tree" or "O Evergreen". The original German lyrics by Ernst Anschütz were written in 1824.
Doc 5: O Christmas Tree - centuries old history. Despite its title, the popular carol O, Christmas Tree was not originally a Christmas song.