Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
cau tren » cu tren, dau tren, ca tren
tang xa » trang xa, lang xa, tang ha
tang ma » mang may, tang van
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan, thuc day
dan tai » van tai, dan thi, han tai
tai cau » tai cac, tai cao
va nam » van nam, ha nam, va nay
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 ky ((tang xa) or (tang ma)) hoi. hieu va nam thuc va dan tai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky ((tang xa) OR (tang ma)) hoi. hieu va nam thuc va dan tai cau tren.
• Adding a wildcard symbol may retrieve word variants: toc sach ky ((tang xa) or (tang ma)) hoi. hieu va nam thuc va dan tai cau tren*.