Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
toc sac » toc san, hoc sach, doc sach
thuc va » thuc vat, thuc dan, thuc day
hieu va » lieu va, hieu qua
lang ha » long ha
ky lang » ky nang, ky dang, ky tang
ha hoi » hoa hoi, ha noi, xa hoi
va dan » ca dan, va dao, va dau
va cuu » va cau, va huu
va chu » va che, va cau, va chi
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 sac) OR (toc sach)) ky lang ha hoi. hieu va nam thuc va dan ((va cuu) or (va chu)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sac) OR (toc sach)) ky lang ha hoi. hieu va nam thuc va dan ((va cuu) OR (va chu)) tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sac) OR (toc sach)) ky lang ha hoi. hieu va nam thuc va dan ((va cuu) or (va chu)) tre*".