Perhaps you should try some spelling variations:
hanh doi » thanh doi, hanh noi, hang doi
thuc day » thuc dan
su sach » so sach, vu sach
doi cua » dai cua, hoi cua
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
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) OR (thuc vat)) hanh doi 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) OR (thuc vat)) hanh doi 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) OR (thuc vat)) hanh doi cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach y ((nang xa) or (nang ma)) hoi. hieu ve cam ((thuc day) OR (thuc vat)) hanh doi cua tre*.