Perhaps you should try some spelling variations:
viet tech » viet sach
hieu viet » sieu viet, hieu viec, lieu viet
tech nuoc » dich nuoc, sach nuoc
vu sach » vu bach, su sach, vu khach
sach ky » sac ky, sach y, sach ty
va danh » va dinh, va dan, va hanh
ma hoi » mai hoi, ma hoa, me hoi
di cua » doi cua, de cua, do cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach ky nang ((ma hoi) or (xa hoi)). hieu viet tech nuoc va danh ((di cua) OR (dai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ky nang ((ma hoi) OR (xa hoi)). hieu viet tech nuoc va danh ((di cua) OR (dai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach ky nang ((ma hoi) or (xa hoi)). hieu viet tech nuoc va danh ((di cua) OR (dai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: vu sach ky nang ((ma hoi) or (xa hoi)). hieu viet tech nuoc va danh ((di cua) OR (dai cua)) tre*.