CREATE TABLE table_23515 ("Representative" TEXT, "State" TEXT, "Training" TEXT, "Title" TEXT, "Appointment" TEXT, "Presentation of Credentials" TEXT, "Termination of Mission" TEXT, "Reason" TEXT)

Who trained the representative whose presentation of credentials happened on February 24, 1950?
SELECT "Training" FROM table_23515 WHERE "Presentation of Credentials" = 'February 24, 1950'
SELECT "Training" FROM "table_23515" WHERE "Presentation of Credentials" = 'February 24, 1950'