1. In memoriam Massimo Simonetta 1920–1986

   • G. Favini

   Announcement Pages: 1 - 1

2. A study of hydrogen bond strengths of neutral water clusters (H₂O) _n using modified MNDO

   • S. H. Suck Salk
   • T. S. Chen
   • C. K. Lutrus

   OriginalPaper Pages: 3 - 10

3. Approximate calculation of the matrix elements of Coulomb and exchange operators for the “core” electrons of the atoms Ga through Kr

   • Raffaele Montagnani
   • Oriano Salvetti

   OriginalPaper Pages: 11 - 15

4. Hartree Fock instabilities in the S₄N ₄ ²⁺ dication

   • M. Bénard
   • W. G. Laidlaw

   OriginalPaper Pages: 17 - 24

5. Aromaticity of annulenes and annulene ions with 4v+2 electrons from the viewpoint of the theory of Hartree-Fock instabilities

   • Peter Karadakov
   • Obis Casta¯no

   OriginalPaper Pages: 25 - 34

6. Properties of “structure factor” of characteristic polynomial and a proof of Hosoya-Randić conjectures

   • He Wenchen
   • He Wenjie

   OriginalPaper Pages: 35 - 41

7. One-to-one correspondence between Kekulé and sextet patterns

   • He Wenjie
   • He Wenchen

   OriginalPaper Pages: 43 - 51

8. Combinatorial Clar sextet theory

   • Sherif El-Basil

   OriginalPaper Pages: 53 - 65

9. On the density matrix definition of valency

   • Omar G. Stradella
   • Hugo O. Villar
   • Eduardo A. Castro

   OriginalPaper Pages: 67 - 71