@article{koornwinder:1974:jpa,
    author = {Koornwinder, Tom H.},
     title = {{J}acobi polynomials. {I}{I}. {A}n analytic proof of the product
              formula},
   journal = {SIAM J. Math. Anal.},
    volume = {5},
      year = {1974},
     pages = {125–137},
   mrclass = {33A65},
  mrnumber = {MR0385198 (52 \#6063)},
mrreviewer = {R. P. Soni},
       doi = {10.1137/0505014},
     zblno = {0242.33020}}