The 5th Supplementary Series of the Beilstein Handbook (4th Edition) covers the compounds reported in the primary literature from 1960 up to 1980. Volume 19 deals with heterocyclic compounds containing two or more chalcogen atoms as the only ring-hetero-atoms; in the current series Vol. 19 is subdivided into 12 parts. Subvolume 19/6 continues the coverage of heterocycles containing only two chalcogen ring heteroatoms (Heterocyclic Class: 2 O) and deals with hydroxy-oxo-compounds of general formula in the range CnH2n-16O4 to CnH2n-54O6.