What is the test for establishing joint authorship?

The authors of a joint work have undivided interests in the entire work, which entitle them to use or license the work as they wish, subject to an accounting of profits. See Thomson v. Larson, 147 F.3d 195, 199 (2d Cir. 1998). In the absence of a written agreement establishing joint authorship, the party claiming joint authorship bears the burden of showing that each of the putative joint authors "(1) made independently copyrightable contributions to the work; and (2) fully intended to be co-authors." Id. at 200. The district court found that Africa satisfied the first element but failed to prove the intent element.