http://digilab.ptb.de/vocab/http://digilab.ptb.de/vocab/skos/24AAF-CO PTP http://digilab.ptb.de/vocab/skos/24 AAF-CO Proficiency Testing Program UF http://digilab.ptb.de/vocab/skos/24 AAFCO Proficiency Testing Program UF http://digilab.ptb.de/vocab/skos/24 AAFCO PTP UF http://digilab.ptb.de/vocab/skos/24 The Association of American Feed Control Officials Proficiency Testing Program UF http://digilab.ptb.de/vocab/skos/24 The Association of American Feed Control PTP UF