Perhaps you should try some spelling variations:
cach thoi » cac thoi, cach thuc, cach noi
van khang » van khanh, van thanh, van quang
khang va » hang va, thang va, khang a
thu sach » thuat sach, thuoc sach, thu hoach
dai khoa » da khoa, tai khoa, dac khoa
duc van » duc va, duc tan, duc manh
cac duc » cac du, cao duc, cac dac
hieu ve » hieu va, hieu van
tu sach » su sach, te sach, tu cach
ky lang » ky nang, ky dang, ky tang
cua tre » cua te, cuu tre, cua triet
ve cac » va cac, vien cac
va cua » va chua, via cua, ca cua

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) OR (thu sach)) ky lang ((dai khoa) or (cach thoi)). hieu ve cac duc van khang va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ky lang ((dai khoa) OR (cach thoi)). hieu ve cac duc van khang va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (thu sach)) ky lang ((dai khoa) or (cach thoi)). hieu ve cac duc van khang va cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (thu sach)) ky lang ((dai khoa) or (cach thoi)). hieu ve cac duc van khang va cua tre*.