Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thuc dan » thuc hanh, hoc dan
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
va cuu » va cau, va huu
va chu » va che, va cau, va chi
va am » va lam, va cam

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 am ((thuc dan) OR (thuc vat)) dan ((va cuu) or (va chu)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky lang xa hoi. hieu va am ((thuc dan) OR (thuc vat)) dan ((va cuu) OR (va chu)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky lang xa hoi. hieu va am ((thuc dan) OR (thuc vat)) dan ((va cuu) or (va chu)) tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ky lang xa hoi. hieu va am ((thuc dan) OR (thuc vat)) dan ((va cuu) or (va chu)) tre*.