@article{marston:1999:cos,
    author = {Marston, P. L.},
     title = {Catastrophe optics of spheroidal drops and generalized
              rainbows},
   journal = {J. Quantit. Spec. and Rad. Trans.},
    volume = {63},
      year = {1999},
     pages = {341–351},
       doi = {10.1016/S0022-4073(99)00023-0}}