Perhaps you should try some spelling variations:
cam thuc » am thuc, nam thuc, cam thu
thuc dan » thuc hanh, hoc dan, thuc vat
dan hanh » dang hanh, dan khanh, dan thanh
su sach » so sach, vu sach
nang ma » tang ma, sang ma, nang cao
hieu ve » hieu va, hieu van
doi cua » hoi cua
ve cam » ve cham, ve cac, va cam

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

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