91色情片

Those non-mathematical readers who really want to understand the intricacies
of phenomena such as the rising and setting stars, tides and timekeeping,
calendars and constellations, planetary paths and eclipses need look no further
than the superbly illustrated The Ever-Changing Sky: A Guide to the Celestial
Sphere (Cambridge University Press, 拢24.95, ISBN 0 521 38053 7) by James
B. Kaler.