Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
thuc day » thuc dan, thuc vat
dang vat » dang van, dong vat, dang nhat
cau tren » cu tren, dau tren, ca tren
sach ky » sac ky, sach y, sach ty
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
hieu va » lieu va, hieu qua
dan vai » dan va, dan tai, dan vat
va nam » van nam, ha nam, va nay

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 lang xa hoi. hieu va nam thuc day ((dan vai) or (dang vat)) cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky lang xa hoi. hieu va nam thuc day ((dan vai) OR (dang vat)) cau tren.
• Adding a wildcard symbol may retrieve word variants: toc sach ky lang xa hoi. hieu va nam thuc day ((dan vai) or (dang vat)) cau tren*.