The Encyclopaedia Britannica was an Earth encyclopaedia that the Seventh Doctor kept in Smithwood Manor circa 2030. (PROSE: Warchild) The TARDIS library had at least four volumes of it by the Eighth Doctor's time. (PROSE: Seeing I)
Bernice Summerfield read a complete set of the 1898-1902 edition in a library, actually watching Rand Gemeno from behind it. (PROSE: The Blame of the Nose)
The Seventh Doctor joked that, if he were about to die, he'd produce a list of regrets the size of Encyclopedia Britannica. (PROSE: Timewyrm: Genesys)
Behind the scenes
The Encyclopaedia Brittanica would later be the inspiration for a Gallifreyan encyclopaedia seen in Journey to the Centre of the TARDIS: the Encyclopedia Gallifreya, which, curiously enough, used the American spelling of "encyclopedia".