International Standard Version If I am not an apostle to other people, surely I am one to you, for you are the evidence of my apostolic authority from the Lord.
American Standard Version If to others I am not an apostle, yet at least I am to you; for the seal of mine apostleship are ye in the Lord.
Young's Literal Translation if to others I am not an apostle -- yet doubtless to you I am; for the seal of my apostleship are ye in the Lord.