Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
hanh dao » lanh dao, thanh dat, thanh dam
hanh dai » hanh tai, vanh dai, thanh dat
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
hoi dan » hoa dan, hoc dan, hoi dap
nam hoi » nam khoa
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
cua tre » cua te, cuu tre, cua triet

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