Perhaps you should try some spelling variations:
cam thuc » am thuc, nam thuc, cam thu
day hanh » day nhanh, day thanh, day manh
dao hanh » dao thanh, dang hanh, ban hanh
nang ma » tang ma, sang ma, nang cao
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
su cac » tu cac, su cao, su can
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 cac ky ((nang ma) or (nang x)) hoi. hieu ve cam thuc ((day hanh) OR (dao hanh)) dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su cac ky ((nang ma) OR (nang x)) hoi. hieu ve cam thuc ((day hanh) OR (dao hanh)) dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su cac ky ((nang ma) or (nang x)) hoi. hieu ve cam thuc ((day hanh) OR (dao hanh)) dai cua tre".
• Adding a wildcard symbol may retrieve word variants: su cac ky ((nang ma) or (nang x)) hoi. hieu ve cam thuc ((day hanh) OR (dao hanh)) dai cua tre*.