@article{guttmann:1993:spe,
    author = {Guttmann, A. J. and Prellberg, T.},
     title = {Staircase polygons, elliptic integrals, {H}eun functions,
              and lattice {G}reen functions},
   journal = {Phys. Rev. E},
      year = {1993},
    volume = {47},
     pages = {R2233–R2236},
    number = {4},
       doi = {10.1103/PhysRevE.47.R2233}}