Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
sach tay » xach tay, sach hay, sach nay
cau tren » cu tren, dau tren, ca tren
lang van » dang van, tang van, hoang van
lang ha » long ha
hieu ha » hieu hoa, hieu ca, hieu xa
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan, thuc day
dan vai » dan va, dan tai, dan vat
vai cau » va cau, van cau, vai cac
va dan » ca dan, va dao, va dau

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

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