@article{schulten:1976:re,
    author = {Schulten, K. and Gordon, R. G.},
     title = {Recursive evaluation of $3j$- and $6j$- coefficients},
   journal = {Comput. Phys. Comm.},
  fjournal = {Computer Physics Communications},
      year = {1976},
    volume = {11},
    number = {2},
     pages = {269–278},
      note = {Double-precision Fortran provided in 3 parts, $j_1$-recursion for $3j$-coefficients,
              $m_2$-recursion for $3j$-coefficients, and $j_1$-recursion for $6j$-coefficients},
       doi = {10.1016/0010-4655(76)90058-8},
     links = {\URL[Code 1]{http://cpc.cs.qub.ac.uk/summaries/ACWQ},
              \URL[Code 2]{http://cpc.cs.qub.ac.uk/summaries/ACWR},
              \URL[Code 3]{http://cpc.cs.qub.ac.uk/summaries/ACWS}}}