Perhaps you should try some spelling variations:
day thanh » dao thanh, dat thanh, da thanh
day hanh » day nhanh, dao hanh, day manh
cam thuc » am thuc, nam thuc, cam thu
su sach » so sach, vu sach
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va, hieu van
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
di cua » dai cua, doi cua, de cua
ve cam » ve cham, ve cac, va cam

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach y ((nang xa) or (nang ma)) hoi. hieu ve cam thuc ((day hanh) OR (day thanh)) di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y ((nang xa) OR (nang ma)) hoi. hieu ve cam thuc ((day hanh) OR (day thanh)) di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y ((nang xa) or (nang ma)) hoi. hieu ve cam thuc ((day hanh) OR (day thanh)) di cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach y ((nang xa) or (nang ma)) hoi. hieu ve cam thuc ((day hanh) OR (day thanh)) di cua tre*.