1. Editorial

   • A. G. W. Cameron
   • Z. Kopal
   • C. P. Sonett

   EditorialNotes Pages: 3 - 3

2. Physics of the primitive solar accretion disk

   • A. G. W. Cameron

   OriginalPaper Pages: 5 - 40

3. Radiation environment detected by a proportional counter in Earth orbit

   • D. R. Parsignault
   • A. Epstein
   • H. Cohn

   OriginalPaper Pages: 41 - 64

4. Grains accretion processes in a protoplanetary nebula: Effects of the presence of liquid drops

   • A. Coradini
   • G. Magni
   • C. Federico

   OriginalPaper Pages: 65 - 76

5. On the monochromatic brightness variations of comets

   • D. A. Mendis
   • G. D. Brin

   OriginalPaper Pages: 77 - 89

6. The dependence of the frequency spectra of the interplanetary magnetic-field fluctuations on the direction of the mean field

   • Jörn E. Kunstmann

   OriginalPaper Pages: 91 - 104

7. Formation of planetary systems by successive contractions of the solar nebula

   • V. Dyczmons

   OriginalPaper Pages: 105 - 142