@article{10_37236_1677,
     author = {Toufik Mansour and Zvezdelina Stankova},
     title = {321-polygon-avoiding permutations and {Chebyshev} polynomials},
     journal = {The electronic journal of combinatorics},
     year = {2002},
     volume = {9},
     number = {2},
     doi = {10.37236/1677},
     zbl = {1039.05002},
     url = {http://geodesic.mathdoc.fr/articles/10.37236/1677/}
}