Perhaps you should try some spelling variations:
minh khai » minh khue, minh chau, minh chi
khai cua » thai cua, hai cua, khi cua
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
nang ma » sang ma, nang cao, mang may
tang ma » mang may, tang van
qua cai » qua hai, qua cac, qua ca
duc van » duc va, duc manh, duc phan
cua tre » cua te, cuu tre, cua triet

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 ty ((nang ma) OR (tang ma)) hoi. hieu qua cai ((duc van) or (duc tan)) minh khai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((nang ma) OR (tang ma)) hoi. hieu qua cai ((duc van) OR (duc tan)) minh khai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty ((nang ma) OR (tang ma)) hoi. hieu qua cai ((duc van) or (duc tan)) minh khai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((nang ma) OR (tang ma)) hoi. hieu qua cai ((duc van) or (duc tan)) minh khai cua tre*.