[My wife] liked to collect old encyclopedias from second-hand bookstores, and at one point we had eight of them. When I wrote my first historical novel---back in 1980, before I was online---I used them often as a research tool. For instance, I learned that the Bastille was either 90 feet high or 100 feet or 120 feet. This led me to formulate Wilson's 22nd Law: 'Certitude belongs exclusively to those who only look in one encyclopedia.'