What sources did dvorak study in his search for an american music?

Afro-descendant spirituality and typical American music.

Explanation:

     Antonin Dvorák, a member of the so-called nationalist school of the romantic period, has established himself as one of the leading names in 19th-century classical music, and the most representative figure in Czech composition. The son of a modest and large Bohemian family, Dvorák was born in 1841 in Nelahozeves, a small settlement near Prague.

    From 1892 to 1895, Dvorák was director of the New York National Conservatory of Music, where he had contact with black spirituality and typical American music. It was during this period that he composed two of his most famous works: Symphony No. 9 ("New World Symphony") and the Greater F Quartet, known as the "American Quartet", both in 1893.