Perhaps you should try some spelling variations:
vu khach » vu khanh, vu khac, cua khach
nam thuc » nam thuoc, am thuc, nam thu
tinh vai » tinh hai, tinh bai, tinh lai
tinh va » tich va, trinh van, trinh vat
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
ly hang » ly quang
va hoc » van hoc
va nam » van nam, ha nam, va nay

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((vu khach) OR (vay khach)) ly hang va hoc. hieu va nam thuc vat ((tinh vai) or (tinh va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((vu khach) OR (vay khach)) ly hang va hoc. hieu va nam thuc vat ((tinh vai) OR (tinh va)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((vu khach) OR (vay khach)) ly hang va hoc. hieu va nam thuc vat ((tinh vai) or (tinh va)) cua tre".
• Adding a wildcard symbol may retrieve word variants: ((vu khach) OR (vay khach)) ly hang va hoc. hieu va nam thuc vat ((tinh vai) or (tinh va)) cua tre*.