00277nam a2200097Ia 450000500170000000800410001708200160005810000200007424500280009426000570012220250107154750.0241216s9999||||xx |||||||||||||| ||und||  aREF 520 OBS  aPercy, J. R. ed 0aObservers handbook 1980  aCanada.bRoyal astronomical society of Canada.c1979