Cosmos ch. 1 (1980). Sagan denied using the phrase "billions and billions," as caricatured by comedian Johnny Carson, but the above quote approaches that phrase, and Sagan was extremely fond in his writing of the word billion or billions.
Douglas Adams (2012). “The Hitchhiker's Guide to the Galaxy Radio Scripts Volume 2: The Tertiary, Quandary and Quintessential Phases”, p.204, Pan Macmillan