Perhaps you should try some spelling variations:
dao thanh » ban thanh, de thanh, ha thanh
day thanh » dat thanh, da thanh, dam thanh
tro thanh » thi thanh, tai thanh
cam thuc » am thuc, nam thuc, cam thu
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
va cam » va cham, va cac, va cao
nang o » nang co, nang ho, nang ro
di cua » dai cua, doi cua, de cua
o hoi » co hoi, o hoc, o hai

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 nang o hoi. hieu va cam thuc ((((dao thanh) or (tro thanh))) or (day thanh)) di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang o hoi. hieu va cam thuc ((((dao thanh) OR (tro thanh))) OR (day thanh)) di cua tre.
• Adding a wildcard symbol may retrieve word variants: su sach ky nang o hoi. hieu va cam thuc ((((dao thanh) or (tro thanh))) or (day thanh)) di cua tre*.