I found the article can help you.

Hello Arun,

thank you for sharing this very interesting technical question with the RG community. We work in a completely different field or research, organometallic chemistry, but I made the experience that many helpful literature references can easily be found and accessed by directly searching the "Publications" section of RG. Even rather complex terms can be searched. For example, just search for the term "DNA extraction from formaldehyde-fixed tissue" and then click on "Publications":

https://www.researchgate.net/search.Search.html?type=publication&query=DNA%20extraction%20from%20formaldehyde-fixed%20tissue

As you can see, the first suggested article is already a rather useful one:

Comparison of different methods for DNA extraction from formaldehyde fixed tissues

Article Comparison of different methods for DNA extraction from form...

Fortunately this paper has been posted by the authors as public full text on RG. Thus you can freely download it as pdf file.

I hope that this information is useful for you. Good luck with your research work!