1. Carlson, J. A.: Extensions of mixed Hodge structures. Journées de Géometrie Algébrique d’Angers, Juillet 1979/Algebraic Geometry, Angers, 1979, pp. 107–127. Sijthoff & Noordhoff, Alphen aan den Rijn–Germantown, Md. (1980)
2. Cartier, P.: Jacobiennes generalisees, monodromie unipotente et integrales iterees, Seminare Bourbaki, Vol. 1987/88, Asterisque No. 161–162 (1988), Exp. No. 687, 3, pp. 31–52 (1989)
3. Chen, K.T.: Iterated integrals, fundamental groups and covering spaces. Trans. Am. Math. Soc. 206, 83–98 (1975)
4. Chen, K.T.: Reduced Bar Constructions on De Rham Complexes, Algebra, Topology and Category Theory, pp. 19–32. Academic Press, New York (1976)
5. Chen, K.T.: Iterated integrals of differential forms and loop space homology. Ann. Math. 97(2), 217–246 (1973)