Perhaps you should try some spelling variations:
va thanh » gia thanh, ban thanh, va tinh
va hanh » van hanh, va danh, ban hanh
cac luc » cau luc, coc luc, cac nuoc
sach ky » sac ky, sach y, sach kem
hieu va » lieu va, hieu qua
nang ma » tang ma, sang ma, nang cao
sach ty » sach y, sach tu, sach thu
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu ((sach ky) or (sach ty)) nang ma hoi. hieu va cac luc ((va hanh) OR (va thanh)) vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sach ty)) nang ma hoi. hieu va cac luc ((va hanh) OR (va thanh)) vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) or (sach ty)) nang ma hoi. hieu va cac luc ((va hanh) OR (va thanh)) vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sach ty)) nang ma hoi. hieu va cac luc ((va hanh) OR (va thanh)) vi cua tre*.