History of the Encyclopædia Britannica
The Encyclopædia Britannica has been published continuously since 1768, appearing in fifteen official editions. Several editions were amended with multi-volume "supplements" (3rd, 4th/5th/6th), several consisted of previous editions with added supplements (10th, 12th, 13th), and one represented a drastic re-organization (15th).
Source: Wikipedia — History of the Encyclopædia Britannica (CC BY-SA 4.0)