Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
la tren » loai tren, dua tren, dat tren
cac tuc » cac toc, cac tu, cac tac
tu sach » thu sach, su sach, te sach
cu tren » tu tren, dua tren
cao hoi » cau hoi, co hoi, cao hoc
v nang » va nang, vu nang, van nang
y nang » ky nang, ly nang, may nang
tuc va » thuc va, truc va, tuc xa
va dan » ca dan, va dao, va dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ((y nang) or (v nang)) cao hoi. hieu vien cac tuc va dan ca ((la tren) or (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((y nang) OR (v nang)) cao hoi. hieu vien cac tuc va dan ca ((la tren) OR (cu tren)).
• Adding a wildcard symbol may retrieve word variants: tu sach ((y nang) or (v nang)) cao hoi. hieu vien cac tuc va dan ca ((la tren) or (cu tren))*.