Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
su tien » su kien, tu tieng, dau tien
danh ki » danh di, danh kien, danh gia
va danh » va dinh, va dan, va hanh
sach ky » sac ky, sach y, sach ty
cac dac » cac dan, cac dai, cac bac
hieu ve » hieu va, hieu van
su hien » su kien, thu hien, nhu hien
ve cac » va cac, vien cac
dac va » duc va, day va, dat va
ma hoi » mai hoi, ma hoa, me hoi

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