Chat-ho?k Pok-s? ( Yin-ngi : Doctor of Philosophy, kien-chh??n Ph.D.), ko-kip ho?k-ham ch??-yit, thung-song he ho?k-li?t ka-keu chung chui ko-kip ke ho?k-ham. yung-yu yit-pan ngin chhai thai-ho?k pun-kho khi?p ngien-kiu-yen pit-ngia?p, chai-hi chin-hang siong-tong ngien-su ke ngien-siu heu, chhon-pit lun-vun pin thung-ko tap-phien.