I’ve been learning about successful entrepreneurs who happen to be investors—I call them “investor entrepreneurs.” They invest as their full-time profession, but not by working for someone else. I’ve been reading as much as I can about these people, including biographies about them.

 A biography, of course, is written by someone who spends a lot of time learning about their subject—in this case, an investor entrepreneur. They talk to family members and coworkers. They read files. They interview the investor entrepreneur. All to get a better understanding of the life of the person they’re writing about.

Sometimes the author can’t fit everything they learned in the book, or the investor entrepreneur won’t agree to certain information being published. Sometimes these missing pieces of information can clarify what made the person exceptionally successful.

Biography authors sometimes talk about what didn’t make it to print. Whenever I read a well-researched biography, I search for recordings of interviews and speeches the author gave about the book. This simple hack has led to stories and facts that helped me better understand some of the greatest investor entrepreneurs.