Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
hanh dai » hanh tai, hanh dao, vanh dai
dan hanh » dang hanh, dan khanh, dan thanh
tu sach » thu sach, su sach, te sach
cua tre » cua te, cua triet, dua tren
nam hoc » nam moc, nam hoi, am hoc
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
cuu tre » cau tren, cau treo
va nam » van nam, ha nam, va nay

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 (doc sach)) ky lang xa hoi. hieu va nam hoc dan hanh dai ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (doc sach)) ky lang xa hoi. hieu va nam hoc dan hanh dai ((cua tre) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (doc sach)) ky lang xa hoi. hieu va nam hoc dan hanh dai ((cua tre) or (cuu tre))*.