The editors of this 1667AD Missale Romanum weren’t sure who wrote the VEXILLA REGIS hymn, so they wrote this in the margin. (To be fair, the original text by Bishop Fortunatus was greatly altered under Pope Urban VIII.)
Pope Saint Paul VI (3 April 1969): “Although the text of the Roman Gradual—at least that which concerns the singing—has not been changed, the Entrance antiphons and Communions antiphons have been revised for Masses without singing.”