Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
van hanh » van thanh, ban hanh, van anh
thuc van » thuc vat, thuc dan, thuc va
day thuc » dan thuc, cay thuc, dai thuc
vien day » vien dai, vien da, vien xay
su sach » so sach, vu sach
ty hang » ly hang, ty xang, thi hang
ty nang » ky nang, ty xang, ly nang
cua tu » cua tuc, cua su, cua cu

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ((ty nang) or (ty hang)) xa hoi. hieu vien day thuc van hanh vi ((cua te) OR (cua tu))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ty nang) OR (ty hang)) xa hoi. hieu vien day thuc van hanh vi ((cua te) OR (cua tu)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ty nang) or (ty hang)) xa hoi. hieu vien day thuc van hanh vi ((cua te) OR (cua tu))".
• Adding a wildcard symbol may retrieve word variants: su sach ((ty nang) or (ty hang)) xa hoi. hieu vien day thuc van hanh vi ((cua te) OR (cua tu))*.