Perhaps you should try some spelling variations:
nien cac » vien cac, bien cac, hien cac
dien cac » vien cac, dien cuc, dien sach
hanh tai » thanh tai, hang tai, han tai
van hanh » van thanh, ban hanh, van anh
duc van » duc va, duc tan, duc manh
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
cuc tre » duc tre, cua tre, cuu tre
co hoa » co hoat, cho hoa, co hoc
o hoa » do hoa, so hoa, o ha

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoa) OR (co hoa)). thieu ((nien cac) OR (dien cac)) duc van hanh tai cuc tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((o hoa) or (co hoa)). thieu ((nien cac) OR (dien cac)) duc van hanh tai cuc tre~".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoa) or (co hoa)). thieu ((nien cac) OR (dien cac)) duc van hanh tai cuc tre*.