Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
cam thuc » am thuc, nam thuc, cam thu
sach tay » xach tay, sach hay, sach nay
tay tang » tay lang, tay trung, tay quang
hieu va » hieu qua
tang ma » mang may, tang van
thuc va » thuc vat, thuc dan, thuc day
va hang » van hang, va nang, va lang
ma hoi » mai hoi, xa hoi, ma hoa
va cau » van cau, va cac, va cao
va dau » va dao

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach tay tang ma hoi. ((hieu va) OR (lieu va)) cam thuc va hang ((va cau) or (va dau)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach tay tang ma hoi. ((hieu va) OR (lieu va)) cam thuc va hang ((va cau) OR (va dau)) tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach tay tang ma hoi. ((hieu va) OR (lieu va)) cam thuc va hang ((va cau) or (va dau)) tren".
• Adding a wildcard symbol may retrieve word variants: doc sach tay tang ma hoi. ((hieu va) OR (lieu va)) cam thuc va hang ((va cau) or (va dau)) tren*.