Perhaps you should try some spelling variations:
manh hanh » xanh hanh, danh thanh, minh thanh
duc manh » suc manh, duc anh, duc minh
su sach » so sach, vu sach
sach vu » sach va, sach tu, sach uu
su viet » so viet
vu nang » vuc nang, va nang, vu dang
va cam » va cham, va cac, va cao
ma hoi » mai hoi, ma hoa, me hoi
ve cai » va cai, ve cac, ve tai
vi su » va su, ve su, ki su

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 vu nang ((ma hoi) OR (xa hoi)). hieu ((ve cai) or (va cam)) duc manh hanh vi su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach vu nang ((ma hoi) OR (xa hoi)). hieu ((ve cai) OR (va cam)) duc manh hanh vi su viet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach vu nang ((ma hoi) OR (xa hoi)). hieu ((ve cai) or (va cam)) duc manh hanh vi su viet*".