Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cau thuc » cau truc, cuu thuc, can thuc
thuc va » thuc vat, thuc dan, thuc day
doi cua » dai cua, hoi cua
hoc anh » hoc nganh, hoc nhanh, ngoc anh
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
di cua » dai cua, de cua, do cua
va cau » van cau, va cac, va dau
v nang » va nang, vu nang, van nang

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) or (hoc anh)) v nang xa hoi. hieu va cau thuc va hanh ((di cua) OR (doi cua)) te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc anh)) v nang xa hoi. hieu va cau thuc va hanh ((di cua) OR (doi cua)) te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (hoc anh)) v nang xa hoi. hieu va cau thuc va hanh ((di cua) OR (doi cua)) te".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc anh)) v nang xa hoi. hieu va cau thuc va hanh ((di cua) OR (doi cua)) te*.