Perhaps you should try some spelling variations:
"van cua cong san" » "van cua cong tac" (Expand Search), "ban cua cong san" (Expand Search), "han cua cong san" (Expand Search), "nhan cua cong san" (Expand Search)
"van cua cong so" » "ban cua cong so" (Expand Search), "han cua cong so" (Expand Search), "nhan cua cong so" (Expand Search), "van cua cong son" (Expand Search), "van cua cong o" (Expand Search), "van cua cong hoa" (Expand Search)
"dan cua cong so" » "dan cua cong son" (Expand Search), "dan cua cong o" (Expand Search), "dan cua cong hoa" (Expand Search), "dan ca cong so" (Expand Search), "ban cua cong so" (Expand Search), "dan cu cong so" (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: (((("van cua cong so") OR ("dan cua cong so"))) OR ("van cua cong san"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"van cua cong so\") OR (\"dan cua cong so\"))) OR (\"van cua cong san\"))".
• Removing quotes may allow a broader search: (((( van cua cong so ) OR ( dan cua cong so ))) OR ( van cua cong san )).
• Adding a wildcard symbol may retrieve word variants: (((("van cua cong so") OR ("dan cua cong so"))) OR ("van cua cong san"))*.