Perhaps you should try some spelling variations:
qua pham » quan pham, quy pham, qua cham
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
sach vu » sach va, sach tu, sach uu
vu nang » vuc nang, va nang, vu dang
nang ma » tang ma, sang ma, nang cao
duc van » duc va, duc tan, duc manh
hanh ki » hanh vi, hanh ky, hanh kien
su tien » su hien, tu tieng, dau tien
kien » bien, vien, dien

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 vu nang ma hoa. hieu qua pham duc van hanh ki ((su tien) or (su kien))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach vu nang ma hoa. hieu qua pham duc van hanh ki ((su tien) OR (su kien)).
• Adding a wildcard symbol may retrieve word variants: tu sach vu nang ma hoa. hieu qua pham duc van hanh ki ((su tien) or (su kien))*.