16. C. Wentrup, P. Müller,
    “One-step syntheses of fulvene and fulvenallen: Thermolysis of α-coumaranone, phthalide, and benzocyclopropene”
    Tetrahedron Lett. 1973, 14, 2915-2918.

DOI : 10.1016/S0040-4039(01)96281-1