@article {ClMa2002,
    author = {Claesson, Anders and Mansour, Toufik},
     title = {Counting occurrences of a pattern of type {$(1,2)$} or
              {$(2,1)$} in permutations},
   journal = {Adv. in Appl. Math.},
  fjournal = {Advances in Applied Mathematics},
    volume = {29},
      year = {2002},
    number = {2},
     pages = {293--310},
      issn = {0196-8858},
       doi = {10.1016/S0196-8858(02)00012-X},
       url = {https://doi.org/10.1016/S0196-8858(02)00012-X},
}