Gennady Pospelov, Walter Van Herck, Jan Burle, Juan M. Carmona Loaiza, Céline Durniak, Jonathan M. Fisher, Marina Ganeva, Dmitry Yurov and Joachim Wuttke (2020):

BornAgain: software for simulating and fitting grazing-incidence small- angle scattering

J. Appl. Cryst. 53, 262–276.

This is the standard reference for BornAgain, see also how to cite.