Perhaps you should try some spelling variations:
mai khoi » mai khoa, tai khoa, cac khoi
van hanh » van thanh, ban hanh, van anh
su sach » so sach, vu sach
ky sang » ky dang, ky tang, duy sang
hieu va » lieu va, hieu qua
cac thu » cach thuc, cac thoi
thu van » thuc van, thuy van, tu van
vai cua » hai cua, lai cua, bai cua

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 ((ky sang) or (ky nang)) mai khoi. hieu va cac thu van hanh ((vai cua) OR (dai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ky sang) OR (ky nang)) mai khoi. hieu va cac thu van hanh ((vai cua) OR (dai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ky sang) or (ky nang)) mai khoi. hieu va cac thu van hanh ((vai cua) OR (dai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: su sach ((ky sang) or (ky nang)) mai khoi. hieu va cac thu van hanh ((vai cua) OR (dai cua)) tre*.