v. 1. Solid sulfur allotropes -- Liquid sulfur -- Speciation and thermodynamics of sulfur vapor -- Homoatomic sulfur cations -- Aqueous sulfur sols -- Biologically produced sulfur -- v. 2. Quantum-chemical calculations of sulfur-rich compounds -- Molecular spectra of sulfur molecules and solid sulfur allotropes -- Inorganic polysulfanes H₂S[n] with n>1 -- Inorganic polysulfides S[n]²⁻ and radical anions S[n]̇⁻ -- Polysulfido complexes of main group and transition metals -- Sulfur-rich oxides S[n]O and S[n]O₂.