Perhaps you should try some spelling variations:
hien xanh » hien hanh, hien nhanh, chieu xanh
dung cong » dung trong
van ranh » van anh, van hanh, van manh
hoc dung » hoc ung, hoc dan, tac dung
cong van » cong vang, cong san, song van
van tai » von tai, van tuan
tai tap » bai tap, tai tao, hai tap

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc hien xanh - ((canh tranh) or (van ranh)) hoc dung cong van tai tap~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc hien xanh - ((canh tranh) OR (van ranh)) hoc dung cong van tai tap.
• Adding a wildcard symbol may retrieve word variants: hoc hien xanh - ((canh tranh) or (van ranh)) hoc dung cong van tai tap*.