Perhaps you should try some spelling variations:
vanh dai » van dai, vanh tai, lanh dao
vu sach » vu bach, su sach, vu khach
va vanh » va van, va danh, va hanh
cau luc » cau truc, cau phuc
cac luc » coc luc, cac nuoc, cac cuoc
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
mang xa » lang xa, mang may, dang xay
cua tre » cua te, cuu tre, cua triet

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 ((mang xa) or (nang ma)) hoi. hieu qua ((cac luc) OR (cau luc)) va vanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ky ((mang xa) OR (nang ma)) hoi. hieu qua ((cac luc) OR (cau luc)) va vanh dai cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach ky ((mang xa) or (nang ma)) hoi. hieu qua ((cac luc) OR (cau luc)) va vanh dai cua tre*".