The main reference to the CAPD library is the following article

T. Kapela, M. Mrozek, D. Wilczak, P. Zgliczynski,
CAPD::DynSys: a flexible C++ toolbox for rigorous numerical analysis of dynamical systems,
Communications in Nonlinear Science and Numerical Simulation, Volume 101, October 2021, 105578. https://doi.org/10.1016/j.cnsns.2020.105578

One may also consider to cite articles, where some of important algorithms implemented in the CAPD library have been developed.