Perhaps you should try some spelling variations:
cam thuc » am thuc, nam thuc, cam thu
hang doi » hang di, hang loi, huong doi
hanh doi » thanh doi, hanh noi, hanh moi
thuc van » thuc vat, thuc dan, thuc va
so sach » so sanh, bo sach, co sach
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va, hieu van
mang xa » lang xa, mang may, dang xay
sach v » sach va, sach y, sach 2
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: so sach v ((mang xa) or (nang x)) hoi. hieu ve cam thuc van ((hanh doi) OR (hang doi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach v ((mang xa) OR (nang x)) hoi. hieu ve cam thuc van ((hanh doi) OR (hang doi)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach v ((mang xa) or (nang x)) hoi. hieu ve cam thuc van ((hanh doi) OR (hang doi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach v ((mang xa) or (nang x)) hoi. hieu ve cam thuc van ((hanh doi) OR (hang doi)) cua tre*.