@article{10_1017_S0017089500008314,
     author = {Peetre, Jaak and Zhang, Genkai},
     title = {Projective structures on an annulus and {Hankel} forms},
     journal = {Glasgow mathematical journal},
     pages = {247--266},
     year = {1991},
     volume = {33},
     number = {3},
     doi = {10.1017/S0017089500008314},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089500008314/}
}