Perhaps you should try some spelling variations:
cau thuc » cau truc, cuu thuc, can thuc
thuc van » thuc vat, thuc dan, thuc va
hanh vai » hanh vi, hanh tai, hanh van
hieu van » hieu va, thien van, lieu va
hanh va » hang va, hanh vi
tu sach » thu sach, su sach, te sach
van cau » van dau, van hau, van chat
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 (thu hoach)) ky lang xa hoi. hieu van cau thuc van ((hanh vai) OR (hanh va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu hoach)) ky lang xa hoi. hieu van cau thuc van ((hanh vai) OR (hanh va)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu hoach)) ky lang xa hoi. hieu van cau thuc van ((hanh vai) OR (hanh va)) cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu hoach)) ky lang xa hoi. hieu van cau thuc van ((hanh vai) OR (hanh va)) cua tre*.