CREATE TABLE table_19031 ("Year" FLOAT, "Mens singles" TEXT, "Womens singles" TEXT, "Mens doubles" TEXT, "Womens doubles" TEXT, "Mixed doubles" TEXT)

who is the the mens singles with mens doubles being kaj lindfors kaj osterberg
SELECT "Mens singles" FROM table_19031 WHERE "Mens doubles" = 'Kaj Lindfors Kaj Osterberg'
SELECT "Mens singles" FROM "table_19031" WHERE "Mens doubles" = 'Kaj Lindfors Kaj Osterberg'