Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
cau theo » cau tao
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan, thuc day
sach ky » sac ky, sach y, sach ty
dan vai » dan tai, dan vat, den vai
dan va » doan va, dan ca, ban va
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 va ((dan vai) or (dan va)) ((cau theo) OR (cau thi))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky lang xa hoi. hieu va nam thuc va ((dan vai) OR (dan va)) ((cau theo) OR (cau thi)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky lang xa hoi. hieu va nam thuc va ((dan vai) or (dan va)) ((cau theo) OR (cau thi))".
• Adding a wildcard symbol may retrieve word variants: toc sach ky lang xa hoi. hieu va nam thuc va ((dan vai) or (dan va)) ((cau theo) OR (cau thi))*.