Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
phan duc » pham duc, phan tu, phan dau
va hanh » van hanh, va thanh, va danh
hieu ve » hieu va, hieu van
tu sach » thu sach, su sach, te sach
ty nang » ky nang, ty hang, ly nang
ve phan » va phan, ke phan, ve phat
va dan » ca dan, va dao, va dau
ve su » va su

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 ((ty nang) OR (ty xang)) xa hoi. hieu ve phan duc ((va hanh) or (va dan)) ve su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ty nang) OR (ty xang)) xa hoi. hieu ve phan duc ((va hanh) OR (va dan)) ve su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ty nang) OR (ty xang)) xa hoi. hieu ve phan duc ((va hanh) or (va dan)) ve su triet".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ty nang) OR (ty xang)) xa hoi. hieu ve phan duc ((va hanh) or (va dan)) ve su triet*.