You can check the following links to search for the chemical and physical properties of pharmaceuticals:

-https://pubchem.ncbi.nlm.nih.gov/search/

-https://toxnet.nlm.nih.gov/

-https://www.drugbank.ca/

There might be many more links, but I get required info. from above links.

Actually these websites are already my references they are good but some times I find some differences between them, that why I ask for a written reference

I don't think there can be a better reference then these, as these are from NIH. Other options are to go through US-FDA or EMA website, download the documents for that particular drug from there, and then get the desired information from there.

-https://www.accessdata.fda.gov/scripts/cder/daf/

-https://www.ema.europa.eu/en/medicines

If these still don't serve your purpose, go to pharmacy/chemistry department of your university, and ask them about some catalogs/encyclopedias which compile such information as hard copies.

That will be fine, thank you very much