During work I have already mentioned several web pages or applications that have helped me to do the job.
Anyway, I would like to remember the ones that have helped me the most:

-Neocities- the page where I hang the project

-Exelearning: the page on which I design the project

-Google scholar- where I look for all the articles or more serious data (I have cited articles in most sections)

-JS9- Where did I get the spectra (only the ones that had Chandra records)

-Simbad: where I got all the photometries.

-Harvard's exoplanets page- where I did research on exoplanets

-Excel- where I made the graph of the Cepheids.

In my opinion, these are the most important pages, software or applications, although there are still many others to mention.