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.
You can refer to The United States Pharmacopeia (USP) or British Pharmacopoeia for reference.
There is other book called Remington practice of pharmacy can also partially solve the issue.
The best option would be the drug information provided in the USFDA Accessdata site or EMC Summary of product characteristics and PubChem site as the information provided here are supposed to be most accurate legally for any particular molecule.