The CCL is still under development and should be considered research in progress. You are welcome to re-use the code, which is open source and available under terms consistent with BSD 3-Clause licensing. If you make use of any of the ideas or software in this package in your own research, please cite them as “(LSST DESC, in preparation)” and provide a link to this repository: https://github.com/LSSTDESC/CCL. For free use of the CLASS library, the CLASS developers require that the CLASS paper be cited: CLASS II: Approximation schemes, D. Blas, J. Lesgourgues, T. Tram, arXiv:1104.2933, JCAP 1107 (2011) 034. The CLASS repository can be found in http://class-code.net. If you have comments, questions, or feedback, please write us an issue. Finally, CCL uses code from the FFTLog package. We have obtained permission from the FFTLog author to include modified versions of his source code.