Perhaps you should try some spelling variations:
cach thoi » cac thoi, cach thuc, cach noi
tan khang » van khang, tao khang, tinh khang
dai khoa » da khoa, tai khoa, dac khoa
khang va » hang va, thang va, khang a
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
ky lang » ky nang, ky dang, ky tang
hieu ve » hieu va, hieu van
cac duc » cac du, cao duc, cac dac
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 ky lang ((dai khoa) or (cach thoi)). hieu ve cac duc tan khang va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky lang ((dai khoa) OR (cach thoi)). hieu ve cac duc tan khang va cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky lang ((dai khoa) or (cach thoi)). hieu ve cac duc tan khang va cua tre*.