Perhaps you should try some spelling variations:
pham thuc » phap thuc, pham chuc, nham thuc
nang cau » nang cao, hang cau, nang dau
hieu van » hieu va, thien van, lieu va
van pham » san pham, van phan, van phat
thuc day » thuc dan, thuc vat
day hanh » day nhanh, day thanh, dao hanh
hanh doi » thanh doi, hanh noi, hang doi
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 van pham thuc day hanh 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 van pham thuc day hanh doi cua tre.
• Adding a wildcard symbol may retrieve word variants: thu ((sach ky) or (sach y)) nang cau hoi. hieu van pham thuc day hanh doi cua tre*.