Qiao, C. The existence and distribution of photon spheres near spherically symmetric black holes: A geometric analysis. SpringerOpen.
Chicago Style (17th ed.) CitationQiao, Chen-Kai. The Existence and Distribution of Photon Spheres Near Spherically Symmetric Black Holes: A Geometric Analysis. SpringerOpen.
MLA (9th ed.) CitationQiao, Chen-Kai. The Existence and Distribution of Photon Spheres Near Spherically Symmetric Black Holes: A Geometric Analysis. SpringerOpen.
Warning: These citations may not always be 100% accurate.