1. S. Axelrod and I. M. Singer, Chern-Simons Perturbation Theory, M.I.T. preprint, October, 1991.
2. D. Bar-Natan, On the Vassiliev Knot Invariants, Harvard preprint, August, 1992.
3. D. Bessis, C. Itzykson, and J.-B. Zuber, Quantum field theory techniques in graphical enumeration, Adv. Appl. Math. 1 (1980), 109–157.
4. M. Culler and K. Vogtmann, Moduli of graphs and automorphisms of free groups, Invent. Math. 84 (1986), 91–119.
5. V. G. Drinfel’d, Quasi-Hopf algebras, Leningrad Math. J. 1 (1990), 1419–1457.