Maurer, Willi (1975), "On most effective tournament plans with fewer games than competitors", The Annals of Statistics, 3 (3): 717–727, doi:10.1214/aos/1176343135, JSTOR2958441, MR0371712.
This equivalence between trees and elements of the free commutative magma on one generator is stated to be "well known and easy to see" by Rosenberg, I. G. (1986), "Structural rigidity. II. Almost infinitesimally rigid bar frameworks", Discrete Applied Mathematics, 13 (1): 41–59, doi:10.1016/0166-218X(86)90068-5, MR0829338.
Cyvin, S. J.; Brunvoll, J.; Cyvin, B.N. (1995), "Enumeration of constitutional isomers of polyenes", Journal of Molecular Structure: THEOCHEM, 357 (3): 255–261, doi:10.1016/0166-1280(95)04329-6.
Maurer, Willi (1975), "On most effective tournament plans with fewer games than competitors", The Annals of Statistics, 3 (3): 717–727, doi:10.1214/aos/1176343135, JSTOR2958441, MR0371712.
This equivalence between trees and elements of the free commutative magma on one generator is stated to be "well known and easy to see" by Rosenberg, I. G. (1986), "Structural rigidity. II. Almost infinitesimally rigid bar frameworks", Discrete Applied Mathematics, 13 (1): 41–59, doi:10.1016/0166-218X(86)90068-5, MR0829338.
Maurer, Willi (1975), "On most effective tournament plans with fewer games than competitors", The Annals of Statistics, 3 (3): 717–727, doi:10.1214/aos/1176343135, JSTOR2958441, MR0371712.