Perhaps you should try some spelling variations:
nhieu viec » hieu viec, nhien viet
trinh vat » trinh van, trinh luat, sinh vat
viec cam » viec lam, viec cua, viec va
vat cua » mat cua, bat cua, dat cua
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
sac ky » cac ky, sai ky
luc va » duc va, loc va
tuc va » thuc va, truc va, tuc xa
tu sac » tu sach, tu cac, tu san

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky ((nang xa) OR (nang ma)) hoi. nhieu viec cam ((luc va) OR (tuc va)) trinh vat cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky ((nang xa) or (nang ma)) hoi. nhieu viec cam ((luc va) OR (tuc va)) trinh vat cua tre~".
• Adding a wildcard symbol may retrieve word variants: tu sac ky ((nang xa) or (nang ma)) hoi. nhieu viec cam ((luc va) OR (tuc va)) trinh vat cua tre*.