Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
nam thuc » nam thuoc, am thuc, nam thu
vat hang » van hang, dat hang, va hang
vu sach » vu bach, su sach, vu khach
hieu va » lieu va, hieu qua
cuu tre » cua tre, cau tren, cau treo
nang o » nang co, nang ho, nang ro
va nam » van nam, ha nam, va nay
va cuu » va cau, va chu, va huu
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: ((vu sach) or (((toc sach) OR (doc sach)))) ky nang o hoi. hieu va nam thuc vat hang va cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((vu sach) OR (((toc sach) OR (doc sach)))) ky nang o hoi. hieu va nam thuc vat hang va cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((vu sach) or (((toc sach) OR (doc sach)))) ky nang o hoi. hieu va nam thuc vat hang va cuu tre".
• Adding a wildcard symbol may retrieve word variants: ((vu sach) or (((toc sach) OR (doc sach)))) ky nang o hoi. hieu va nam thuc vat hang va cuu tre*.