Perhaps you should try some spelling variations:
thuat san » thuat toan, thuat song, thuat lanh
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
hanh di » hanh vi, hanh de, hang di
ma hanh » va hanh, da hanh, na hanh
thuc ma » thuoc ma, thuc va, thuc ha
ky tang » ky nang, ky dang, kho tang
ky lang » ky nang, ky dang, tay lang
cua tre » cua te, cuu tre, cua triet
di cua » dai cua, doi cua, de cua

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 (thuat san)) ((ky lang) OR (ky tang)) xa hoi. hieu van nam thuc ma hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thuat san)) ((ky lang) OR (ky tang)) xa hoi. hieu van nam thuc ma hanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thuat san)) ((ky lang) OR (ky tang)) xa hoi. hieu van nam thuc ma hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thuat san)) ((ky lang) OR (ky tang)) xa hoi. hieu van nam thuc ma hanh di cua tre*.