Perhaps you should try some spelling variations:
"cong tac nhung van." » "cong thuc nhung van." (Expand Search), "cong dac nhuong van." (Expand Search), "cong truc nhung van." (Expand Search), "dong tac nhung van." (Expand Search)
"cong tac dung van." » "cong tac dong van." (Expand Search), "cong tac trung van." (Expand Search), "cong ap dung van." (Expand Search), "cong tac song van." (Expand Search), "dong tac dung van." (Expand Search)
"cong tac dung va." » "cong tac dong va." (Expand Search), "cong tac trung va." (Expand Search), "cong ap dung va." (Expand Search), "dong tac dung va." (Expand Search)

Try widening your search to All Fields.

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

• Performing a fuzzy search may retrieve terms with similar spellings: (((("cong tac dung van.") OR ("cong tac nhung van."))) OR ("cong tac dung va."))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"cong tac dung van.\") OR (\"cong tac nhung van.\"))) OR (\"cong tac dung va.\"))".
• Removing quotes may allow a broader search: (((( cong tac dung van. ) OR ( cong tac nhung van. ))) OR ( cong tac dung va. )).
• Adding a wildcard symbol may retrieve word variants: (((("cong tac dung van.") OR ("cong tac nhung van."))) OR ("cong tac dung va."))*.