For a thorough survey of the history of formal modal logic and of the associated mathematics, see Robert Goldblatt (2006).
Robert Goldblatt (1984) Topoi, the Categorial Analysis of Logic (Studies in logic and the foundations of mathematics, 98).
Robert Louis Stevenson | Robert De Niro | Robert E. Lee | Robert Mugabe | Robert Redford | Robert Burns | Robert Bosch GmbH | Robert | Robert A. Heinlein | Robert Schumann | Robert Browning | Robert Rauschenberg | Robert Plant | Robert Altman | Robert Mitchum | Robert Frost | Robert Southey | Robert F. Kennedy | Robert Maxwell | Robert Graves | Robert E. Howard | Robert Fripp | Robert Fisk | Robert Rodriguez | Robert Motherwell | Robert Lowell | Robert Johnson | Robert Duvall | Robert Boyle | Robert Walpole |