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

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 sach)) v nang xa hoi. hieu va cau truc 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 sach)) v nang xa hoi. hieu va cau truc 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 sach)) v nang xa hoi. hieu va cau truc va hanh ((di cua) OR (doi cua)) te".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) v nang xa hoi. hieu va cau truc va hanh ((di cua) OR (doi cua)) te*.