Thanks, I wonder if I can email the author and ask him for a source. I tried finding the email of the author to no avail.

Edit: I found their University Profile and sent them an email

The email:

Distinguished Professor Moore,

In your book “Fidel Castro: In His Own Words”, you cited the following quote from Fidel: “I began revolution with 82 men. If I had to do it again, I’d do it with 10 or 15 and absolute faith. It does not matter how small you are if you have faith and plan of action”. However, you did include a source of the quote.

I have been unsuccessful in locating the source of this quote. I would really appreciate if you helped me out by providing me with the source.

Thank you so much for time and effort,