A Trous Wavelets Transformation Layer Documentation

Hello, could you please recommend me some documentation on the operation and content of A Trous Wavelet layers?

I recently created a Siril command script to “automate” the processing of an already integrated image by manipulating the Wavelets layers generated by Siril… it has given me good results and I want to go deeper into A Trous Wavelet layers and I can’t find adequate documentation.

Thanks