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