Institution: | (1) Harvard College Observatory and Smithsonian Astrophysical Observatory, Cambridge, Mass., USA;(2) Observatory Sonnenborgh, Utrecht, The Netherlands;(3) O. Schmidt Institute of Physics of the Earth, U.S.S.R. Academy of Sciences, Moscow, U.S.S.R.;(4) Observatoire de Paris, Meudon, France;(5) Harvard College Observatory, Cambridge, Massachusetts, USA |