Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
cam thuc » am thuc, nam thuc, cam thu
vat hanh » vat thanh, van hanh, va hanh
sach ty » sach y, sach tu, sach thu
ty tang » tay tang, ty xang, ty hang
tang ma » mang may, tang van
hieu ve » hieu va, hieu van
hanh va » hang va, hanh vi
cuu tre » cua tre, cau tren, cau treo
ma hoi » mai hoi, xa hoi, ma hoa
va cuu » va cau, va chu, va huu
lien » bien, vien, tien

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sach ty tang ma hoi. ((((hieu ve) or (hieu qua))) or (lien quan)) cam thuc vat hanh va cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ty tang ma hoi. ((((hieu ve) OR (hieu qua))) OR (lien quan)) cam thuc vat hanh va cuu tre.
• Adding a wildcard symbol may retrieve word variants: hoc sach ty tang ma hoi. ((((hieu ve) or (hieu qua))) or (lien quan)) cam thuc vat hanh va cuu tre*.