Perhaps you should try some spelling variations:
"van cua cong san" » "van cua cong tac" (Expand Search), "ban cua cong san" (Expand Search), "dan cua cong san" (Expand Search), "nhan cua cong san" (Expand Search)
"han cua cong san" » "han cua cong tac" (Expand Search), "nhan cua cong san" (Expand Search), "than cua cong san" (Expand Search), "ban cua cong san" (Expand Search)
"van cua cong so" » "ban cua cong so" (Expand Search), "dan 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)

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 ((("van cua cong san") OR ("han cua cong san"))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"van cua cong so\") OR (((\"van cua cong san\") OR (\"han cua cong san\"))))".
• Removing quotes may allow a broader search: (( van cua cong so ) OR ((( van cua cong san ) OR ( han cua cong san )))).
• Adding a wildcard symbol may retrieve word variants: (("van cua cong so") OR ((("van cua cong san") OR ("han cua cong san"))))*.