Perhaps you should try some spelling variations:
vat thanh » dat thanh, gat thanh, tat thanh
cam thuc » am thuc, nam thuc, cam thu
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
tang ma » mang may, tang van
nang ma » sang ma, nang cao, mang may
ve cam » ve cham, ve cac, va cam
va cua » va chua, via cua, ca cua
va chu » va che, va cau, va chi

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 ky ((nang ma) or (tang ma)) hoi. hieu ve cam thuc vat thanh ((va cua) or (va chu)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang ma) OR (tang ma)) hoi. hieu ve cam thuc vat thanh ((va cua) OR (va chu)) tre.
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang ma) or (tang ma)) hoi. hieu ve cam thuc vat thanh ((va cua) or (va chu)) tre*.