5,5-system with a bridgehead nitrogen atom / P. Paolini -- Indolizine and aza derivatives with additional nitrogens in the 5-membered ring / H.L. Blewitt -- Azaindolizine systems having more than one nitrogen atom in the 6-membered ring / Georges Mauey -- The chemistry of cyclazines / Alfred Taurins -- Dithiole and dithiolium systems / R.D. Hamilton and E. Campaigns -- Heteropentalenes / K.T. Potts -- Borazaromatic compounds / Albert J. Fritsch -- Syntheses and properties of cyanine and related dyes / David M. Sturmer.