Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
tu sach » thu sach, su sach, tu cach
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
cau tuc » cau truc, cau tu, cau luc
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
va cau » van cau, va cac, va dau
tuc va » thuc va, truc va, tuc xa
vi cua » vai cua, di cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (((te sach) OR (toc sach)))) ky nang xa hoi. hieu va cau tuc va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (((te sach) OR (toc sach)))) ky nang xa hoi. hieu va cau tuc va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (((te sach) OR (toc sach)))) ky nang xa hoi. hieu va cau tuc va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (((te sach) OR (toc sach)))) ky nang xa hoi. hieu va cau tuc va hanh vi cua tre*.