Decaying vacuum flat cosmological models - Expressions for some observable quantities and their properties

Flat cosmological models with a cosmological term varying as Lambda = (alpha)(R exp -2) + (beta)(H squared) + gamma are investigated. Exact expressions for observable quantities are obtained and some of their properties discussed. The lookback time-redshift, the luminosity distance-redshift, the angular diameter distance-redshift, and the comoving volume derivative-redshift diagrams for some selected world models are also presented.