Perhaps you should try some spelling variations:
hieu viet » hieu viec, lieu viet, tieu viet
tech nuoc » dich nuoc, sach nuoc
sieu viet » su viet, dien viet, bien viet
vu sach » vu bach, vu khach
danh di » danh du, xanh di, danh dien
va danh » va dinh, va dan, va hanh
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, sang ma, nang cao
su sach » so sach
ma hoi » mai hoi, xa hoi, ma hoa
di cua » dai cua, doi cua, de 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) or (su sach)) ky nang ma hoi. ((hieu viet) OR (sieu viet)) tech nuoc va danh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((vu sach) OR (su sach)) ky nang ma hoi. ((hieu viet) OR (sieu viet)) tech nuoc va danh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((vu sach) or (su sach)) ky nang ma hoi. ((hieu viet) OR (sieu viet)) tech nuoc va danh di cua tre".
• Adding a wildcard symbol may retrieve word variants: ((vu sach) or (su sach)) ky nang ma hoi. ((hieu viet) OR (sieu viet)) tech nuoc va danh di cua tre*.