Perhaps you should try some spelling variations:
pham thuc » phap thuc, pham chuc, nham thuc
day thanh » dao thanh, dat thanh, da thanh
day hanh » day nhanh, dao hanh, day manh
nang cau » nang cao, hang cau, nang dau
hieu va » lieu va, hieu qua
va pham » van pham, va phat, va phap
sach ky » sac ky, sach ty, sach kem
doi cua » dai cua, hoi cua
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: thu ((sach ky) or (sach y)) nang cau hoi. hieu va pham thuc ((day hanh) OR (day thanh)) doi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach ky) OR (sach y)) nang cau hoi. hieu va pham thuc ((day hanh) OR (day thanh)) doi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach ky) or (sach y)) nang cau hoi. hieu va pham thuc ((day hanh) OR (day thanh)) doi cua tre".
• Adding a wildcard symbol may retrieve word variants: thu ((sach ky) or (sach y)) nang cau hoi. hieu va pham thuc ((day hanh) OR (day thanh)) doi cua tre*.