Ernst, C.; Sumners, D. W. (November 1990). "A calculus for rational tangles: applications to DNA recombination". Mathematical Proceedings of the Cambridge Philosophical Society. 108 (3): 489–515. Bibcode:1990MPCPS.108..489E. doi:10.1017/s0305004100069383. ISSN0305-0041.
Ernst, C.; Sumners, D. W. (November 1990). "A calculus for rational tangles: applications to DNA recombination". Mathematical Proceedings of the Cambridge Philosophical Society. 108 (3): 489–515. Bibcode:1990MPCPS.108..489E. doi:10.1017/s0305004100069383. ISSN0305-0041.
Ernst, C.; Sumners, D. W. (November 1990). "A calculus for rational tangles: applications to DNA recombination". Mathematical Proceedings of the Cambridge Philosophical Society. 108 (3): 489–515. Bibcode:1990MPCPS.108..489E. doi:10.1017/s0305004100069383. ISSN0305-0041.