Perhaps you should try some spelling variations:
khoan pho » khoan nhoi, khoan phai, khoan hoi
pho thong » he thong
sanh tri » thanh tri, dinh tri, minh tri
sach dai » sach dao, sach bai, sach dat
cac khoa » cac khoi, dac khoa, cao khoa
khoa pho » khoa phu, khoa khoa, khoa phau
so sanh » do sanh
tue cac » tu cac, tuc cac, te cac
te sach » toc sach
dai ve » dap ve, dau ve, dai va
ve cac » va cac, vien cac

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (( so sanh tri tue cac khoan pho thong ) or ( te sach dai ve cac khoa pho thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( so sanh tri tue cac khoan pho thong ) OR ( te sach dai ve cac khoa pho thong )).
• Adding a wildcard symbol may retrieve word variants: (( so sanh tri tue cac khoan pho thong ) or ( te sach dai ve cac khoa pho thong ))*.