19. The Lean Startup: How Today's Entrepreneurs Use Continuous Innovation to
Create Radically Successful Businesses (Eric Ries) - http://bit.ly/GetLeanStartup
21. “Make things people want.” - Paul Graham
“One metric for Product/Market Fit is if at least 40% percent of surveyed
customers (Users) indicate that they would be "very disappointed" if
they no longer have access to a particular product or service. “