Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
sach ky » sac ky, sach y, sach kem
sach ty » sach y, sach tu, sach thu
hieu ve » hieu va, hieu van
kem cua » em cua, keo cua, diem cua
cua tre » cua te, cuu tre, cua triet
ve cam » ve cham, ve cac, va cam
cam lo » nam lo, cam ly, cam o
lo van » le van, vo van, so van
x hoi » xa hoi, o hoi, 5 hoi

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: te ((sach ky) or (sach ty)) nang ((x hoi) OR (x ho)). hieu ve cam lo van hanh kem cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach ky) OR (sach ty)) nang ((x hoi) OR (x ho)). hieu ve cam lo van hanh kem cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach ky) or (sach ty)) nang ((x hoi) OR (x ho)). hieu ve cam lo van hanh kem cua tre".
• Adding a wildcard symbol may retrieve word variants: te ((sach ky) or (sach ty)) nang ((x hoi) OR (x ho)). hieu ve cam lo van hanh kem cua tre*.