Perhaps you should try some spelling variations:
pham thuc » phap thuc, pham chuc, nham thuc
nuoc sach » nguoi sach, hoc sach, cuoc cach
doc sach » hoc sach, toc sach, dac sac
cao hoi » cau hoi, co hoi, cao hoc
hieu vi » hieu voi, hieu va, hieu ve
va hanh » van hanh, va thanh, ban hanh
va danh » va dinh, va dan, dia danh
su tien » su kien, su hien, tu tieng
dan su » dang su

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((doc sach) or (nuoc sach)) ky nang cao hoi. hieu vi pham thuc ((va hanh) OR (va danh)) dan su tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((doc sach) OR (nuoc sach)) ky nang cao hoi. hieu vi pham thuc ((va hanh) OR (va danh)) dan su tien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((doc sach) or (nuoc sach)) ky nang cao hoi. hieu vi pham thuc ((va hanh) OR (va danh)) dan su tien".
• Adding a wildcard symbol may retrieve word variants: ((doc sach) or (nuoc sach)) ky nang cao hoi. hieu vi pham thuc ((va hanh) OR (va danh)) dan su tien*.