-
Hall, R. Cargill. Lunar Impact. Washington: National Aeronautics and Space Administration, 1977. ISBN 978-0-486-47757-2. NASA SP-4210.
- One of the wonderful things about the emergence of electronic books is that long out-of-print works from publishers' back-lists are becoming available once again since the cost of keeping them in print, after the initial conversion to an electronic format, is essentially zero. The U.S. civilian space agency NASA is to be commended for their efforts to make publications in their NASA history series available electronically at a bargain price. Many of these documents, chronicling the early days of space exploration from a perspective only a few years after the events, have been out of print for decades and some command forbidding prices on used book markets. Those interested in reading them, as opposed to collectors, now have an option as inexpensive as it is convenient to put these works in their
- hands.