CREATE TABLE table_15774 ("Year" TEXT, "Men's singles" TEXT, "Women's singles" TEXT, "Men's doubles" TEXT, "Women's doubles" TEXT, "Mixed doubles" TEXT)

What year did Lonneke Janssen win the Women's singles?
SELECT "Year" FROM table_15774 WHERE "Women's singles" = 'lonneke janssen'
SELECT "Year" FROM "table_15774" WHERE "Women's singles" = 'lonneke janssen'