Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
phan duc » pham duc, phan tu, phan dau
tu sach » thu sach, su sach, te sach
su tien » su kien, tu tieng, dau tien
duc van » duc va, duc tan, duc manh
va phan » van phan, va phat, va phap
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
nang ma » tang ma, sang ma, nang cao
mang xa » lang xa, mang may, dang xay
su hien » su kien, thu hien, nhu hien

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