Books published by ReBeats, Rob Cook's drum history company, are now available as digital downloads. Many of these are "must have" reference books for vintage drum enthusiasts, especially the ones that Rob Cook authored. Rob is known as one of the top experts about vintage drums and drum companies. He is also the producer of the long running Chicago Drum Show, the largest annual vintage drum gathering. Here's the link: https://hudsonmusic.com/product-category/books/?publisher=rebeats