This is a repository to save some notebooks related to my initial study of CCL and NumCosmo libraries. These notebooks were created around the first semester of 2023. The final notebooks, used in my Master's Thesis at the end of 2023, aren't all available online yet, because I am still working on improvements. However, two of them can be found in (https://github.com/NumCosmo/NumCosmo/tree/xcor_ccl_gal/notebooks/extern_lib_comparisons), the ccl_xcor_dndz.ipynb file and the ccl_xcor_dndz_gaussians.ipynb file.