Perhaps you should try some spelling variations:
cac thuc » cach thuc, cac thu, can thuc
van hanh » van thanh, ban hanh, van anh
thuc van » thuc vat, thuc dan, thuc va
lai cua » dai cua, lai chau, thai cua
hai cua » thai cua, dai cua, hoi cua
hieu ve » hieu va, hieu van
tu dan » tuc dan, tu ban, cu dan
dan ky » van ky
co hoi » co hoc, co loi
ve cac » va cac, vien cac
o hoi » o hoc, o hai, o hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu dan ky nang ((o hoi) OR (co hoi)). hieu ve cac thuc van hanh ((hai cua) or (lai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu dan ky nang ((o hoi) OR (co hoi)). hieu ve cac thuc van hanh ((hai cua) OR (lai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu dan ky nang ((o hoi) OR (co hoi)). hieu ve cac thuc van hanh ((hai cua) or (lai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: tu dan ky nang ((o hoi) OR (co hoi)). hieu ve cac thuc van hanh ((hai cua) or (lai cua)) tre*.