Perhaps you should try some spelling variations:
trinh tai » trinh toan, trinh tu, trinh han
hieu van » hieu va, thien van, lieu va
dang mai » dang hai, dang mau, dang bai
va trinh » van trinh, va tinh, lap trinh
cua tre » cuu tre, cua triet, dua tren
cac duc » cac du, cao duc, cac dac
te sach » toc sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va
mai hoi » mai khoi, dai hoi, lai hoi
ky dang » ky nang, ky danh
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ky dang mai hoi. ((hieu ve) or (hieu van)) cac duc va trinh tai ((cua tre) OR (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky dang mai hoi. ((hieu ve) OR (hieu van)) cac duc va trinh tai ((cua tre) OR (cua te)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky dang mai hoi. ((hieu ve) or (hieu van)) cac duc va trinh tai ((cua tre) OR (cua te))".
• Adding a wildcard symbol may retrieve word variants: te sach ky dang mai hoi. ((hieu ve) or (hieu van)) cac duc va trinh tai ((cua tre) OR (cua te))*.