Thanks Doitsu. One of the books I downloaded was
Blackfeet Indian Stories by George Bird Grinnell. In the Calibre viewer it looks like there is no TOC. Inside the book is an HTML TOC like you said. I don't know much about programming and HTML so I try to muddle around using tools with a GUI interface like Calibre and Sigil to protect me from my own ignorance and help me to achieve my objectives. In this case I was able to convert the book to epub using Calibre and then use Sigil to generate a TOC. Amazingly it worked!
Thank you for the help. I checked out XPath expressions and they look a little intimidating.!!