J. van der Wal. Note on algorithm 21. Computing, 17(3):261-264, 1976. [doi]
@article{Wal76a, title = {Note on algorithm 21}, author = {J. van der Wal}, year = {1976}, doi = {10.1007/BF02259650}, url = {http://dx.doi.org/10.1007/BF02259650}, researchr = {https://researchr.org/publication/Wal76a}, cites = {0}, citedby = {0}, journal = {Computing}, volume = {17}, number = {3}, pages = {261-264}, }