Perhaps you should try some spelling variations:
va thanh » gia thanh, ban thanh, va tinh
hieu van » hieu va, thien van, lieu va
cau duc » cao duc, cau luc, chu duc
sach ky » sac ky, sach y, sach ty
tu sach » thu sach, su sach, te sach
van cau » van dau, van hau, van chat
lam so » lam son, ham so, lam co
nam so » nam sao, nam bo
o lai » o lao
o hai » co hai, so hai, _ hai

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 ky nang ((o hai) OR (o lai)). hieu van cau duc va thanh ((lam so) or (nam so)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hai) OR (o lai)). hieu van cau duc va thanh ((lam so) OR (nam so)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((o hai) OR (o lai)). hieu van cau duc va thanh ((lam so) or (nam so)) triet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hai) OR (o lai)). hieu van cau duc va thanh ((lam so) or (nam so)) triet*.