Perhaps you should try some spelling variations:
phap thuc » phap thu, phap hoc, phap tu
tham hoan » nham hoan, tham hoa, pham hoang
hanh tai » thanh tai, hang tai, han tai
hieu van » hieu va, thien van, lieu va
pham thu » pham thuc, pham thi, pham tu
tai cua » thai cua, tai cuc, tri cua
xa hanh » xa thanh, xa khanh, va hanh
tu sach » thu sach, te sach, tu cach
hoan xa » hoang xa, hoa xa, hoan va
su sach » so sach, vu sach
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 (su sach)) tham hoan xa hoi. hieu van ((pham thu) or (phap thuc)) xa hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) tham hoan xa hoi. hieu van ((pham thu) OR (phap thuc)) xa hanh tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (su sach)) tham hoan xa hoi. hieu van ((pham thu) or (phap thuc)) xa hanh tai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (su sach)) tham hoan xa hoi. hieu van ((pham thu) or (phap thuc)) xa hanh tai cua tre*.