Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach ky » sac ky, sach y, sach ty
mai hoi » mai khoi, dai hoi, lai hoi
va dinh » van dinh, va kinh, va tinh
dinh va » dinh van, dinh ve, tinh va
su viet » so viet
ma hoi » xa hoi, ma hoa, me hoi
va dam » van dam, va dao, va dap
va dau » va dao

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ky nang ((ma hoi) or (mai hoi)). hieu ((va dam) OR (va dau)) tu va dinh va su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang ((ma hoi) OR (mai hoi)). hieu ((va dam) OR (va dau)) tu va dinh va su viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky nang ((ma hoi) or (mai hoi)). hieu ((va dam) OR (va dau)) tu va dinh va su viet".
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang ((ma hoi) or (mai hoi)). hieu ((va dam) OR (va dau)) tu va dinh va su viet*.