Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
tu sach » su sach, te sach, tu cach
cua tre » cua te, cua triet, dua tren
van vat » van chat, nhan vat
cac tac » cac toc, cac bac, cac dac
hieu va » lieu va, hieu qua
cuu tre » cau tren, cau treo
tac va » tac da, tac xa, tuc va
nang o » nang co, nang ho, nang ro
y nang » ky nang, ly nang, v nang
o hoi » co hoi, o hoc, o hai

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 (thu sach)) y nang o hoi. hieu va cac tac va van vat ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) y nang o hoi. hieu va cac tac va van vat ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (thu sach)) y nang o hoi. hieu va cac tac va van vat ((cua tre) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (thu sach)) y nang o hoi. hieu va cac tac va van vat ((cua tre) or (cuu tre))*.