 Although such connections were not found at that time (they later were), the ambitious expedition set new standards for organized cave exploration, and became the subject of Brucker's first book, "The Caves Beyond", which he co-authored with Joe Lawrence, Jr.Convinced that Crystal Cave would one day connect with caves in nearby Mammoth Cave National Park, Brucker and other explorers formed the Cave Research Foundation (CRF), to survey and study Mammoth Cave and other caves in the area.Through the late 1950s and 60s, under the leadership of Brucker and others, CRF expanded the known reaches of Mammoth Cave and other caves under the adjoining Flint Ridge.