Superfluid equation of state of dilute composite bosons or how to include 3-and 4-body problems in the many body problem - Leyronas, X. and Combescot, R. LASER PHYSICS19, 599-601(2009)
Four-particle problem using Feynman diagrams - Brodsky, I. V. and Kagan, M. Yu. and Klaptsov, A. V. and Combescot, R. and Leyronas, X. LASER PHYSICS17, 523-526(2007)