Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nham thu » nham thuc, pham thu, nhan thuc
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
cao hoi » cau hoi, co hoi, cao hoc
va danh » va dinh, va dan, va hanh
vai va » mai va, dai va, lai va
hai va » hai van, thai va, hoi va
thiet » thieu

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky nang cao hoi. hieu van ((nham thu) OR (nam thu)) va danh ((vai va) or (hai va)) thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang cao hoi. hieu van ((nham thu) OR (nam thu)) va danh ((vai va) OR (hai va)) thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang cao hoi. hieu van ((nham thu) OR (nam thu)) va danh ((vai va) or (hai va)) thiet".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang cao hoi. hieu van ((nham thu) OR (nam thu)) va danh ((vai va) or (hai va)) thiet*.