Several reference publications on prominent people
Who's Who (or Who is Who) is the title of a number of reference publications, generally containing concise biographical information on the prominent people of a country. The title has been adopted as an expression meaning a group of notable persons. The oldest and best-known is the annual publication Who's Who, a reference work on contemporary prominent people in Britain published annually since 1849. Notable examples by country. Who's Who, the oldest listing of prominent British people since 1849; people who have died since 1897 are listed in Who Was Who.
https://en.wikipedia.org/wiki/Who%27s_Who