Anything that you read functions in two ways: it teaches you more about your topic, and it gives you clues about where to go to find out more about your topic. In addition to Wikipedia, I've listed two reference collections below that are great starting places. Use these and Wikipedia to learn the vocabulary of your topic (names of scholars, alternate phrasings for the topic itself, and phrasings for related topics) and to mine every bibliography you can find for relevant sources. Track down the bibliography items (using the "finding full text" tab above) and use the vocabulary of your topic to construct more searches.

Another great place to start is a reference source. These are written for an academic audience and the best entries are those that give you clues about where you might look next (other entries, similar names, and especially "further reading").

~or~

The Literary Encyclopedia

Use the vocabulary and names you learned above to search for articles:

Children's literature, Austrian

Children's literature, German

Young adult literature, German