Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuoc sinh
thuat sach » thuat lanh, thuat san
hieu van » hieu va, thien van, lieu va
hang di » hang doi, hang vi, hang dien
va hang » van hang, va nang, va lang
van hac » van hoc, van ha, van hai
cua tre » cua te, cuu tre, cua triet
ty nang » ky nang, ty xang, ty hang
nang o » nang co, nang ho, nang ro
hac du » cac du, han du, hac de
di cua » dai cua, doi cua, de cua
du va » dau va, tu va, su va
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: ((((thu hoach) or (thuoc sach))) or (thuat sach)) ty nang o hoi. hieu van hac du va hang di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((((thu hoach) OR (thuoc sach))) OR (thuat sach)) ty nang o hoi. hieu van hac du va hang di cua tre.
• Adding a wildcard symbol may retrieve word variants: ((((thu hoach) or (thuoc sach))) or (thuat sach)) ty nang o hoi. hieu van hac du va hang di cua tre*.