Wikipedia: Pioneer Venus project - An overview of the Pioneer mission to Venus consisting of two components, launched separately: an Orbiter and a Multiprobe. - http://en.wikipedia.org/wiki/Pioneer_Venus_project
Pioneer Venus Project Information - Mission description and overview, with related links. - http://nssdc.gsfc.nasa.gov/planetary/pioneer_venus.html
Pioneer Venus Orbiter - Spacecraft and mission profile from the National Space Science Data Center. - http://nssdc.gsfc.nasa.gov/nmc/tmp/1978-051A.html