TITLE: Kahler manifolds with constant bisectional curvature
QUESTION [7 upvotes]: It is well known that the universal covering of a complete Kahler manifold with constant bisectional curvature is $\mathbb{C}^n$, $\mathbb{B}^n$ or $\mathbb{CP}^n$. I need original paper(s) that prove this theorem.

REPLY [7 votes]: This is theorem 7.9 in the book of Kobayashi-Nomizu "Foundations of Differential Geometry Vol.II". There the authors attribute it to Hawley and Igusa independently. These are probably the first papers where this result was proved.
Of course, as Robert Bryant points out, the correct assumption is "constant holomorphic sectional curvature".