Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
doc sach » hoc sach, toc sach, nuoc sach
hanh dao » lanh dao, thanh dat, thanh dam
dan hanh » dang hanh, dan khanh, dan thanh
thuc dan » thuc hanh, hoc dan, thuc vat
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
dao cua » dai cua, day cua, dan cua
ky tang » ky nang, ky dang, kho tang
ky lang » ky nang, ky dang, tay lang
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: ((thu sach) or (doc sach)) ((ky lang) or (ky tang)) xa hoi. hieu van nam thuc dan hanh dao cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu sach) OR (doc sach)) ((ky lang) OR (ky tang)) xa hoi. hieu van nam thuc dan hanh dao cua tre.
• Adding a wildcard symbol may retrieve word variants: ((thu sach) or (doc sach)) ((ky lang) or (ky tang)) xa hoi. hieu van nam thuc dan hanh dao cua tre*.