NAVratna companeezz..

Public Sector Enterprises of India

 http://en.wikipedia.org/wiki/Navratna

http://www.businessnewsthisweek.com/2010/05/navratna-companies-most-successful.html

http://www.currentaffairsindia.info/2012/08/navratna-companies-of-india.html

http://www.pbr.co.in/

www.pbr.co.in/vol3iss4/chapter%208.pdf