Perhaps you should try some spelling variations:
"cong tac mo dung tai lieu." » "cong tac mo dong tai lieu." (Expand Search), "cong tac mo dung doi lieu." (Expand Search), "cong tac mo dung tin lieu." (Expand Search), "cong tac my dung tai lieu." (Expand Search), "cong tac mo rung tai lieu." (Expand Search), "cong tac mo cung tai lieu." (Expand Search), "cong toc mo dung tai lieu." (Expand Search), "dong tac mo dung tai lieu." (Expand Search)
"cong tac bao dung tai lieu." » "cong tac bao dong tai lieu." (Expand Search), "cong tac bao dung doi lieu." (Expand Search), "cong tac bao dung tin lieu." (Expand Search), "cong tac bao duong tai lieu." (Expand Search), "cong tac bao dang tai lieu." (Expand Search), "cong tac ban dung tai lieu." (Expand Search), "dong tac bao dung tai lieu." (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 mo dung tai lieu.") OR ("cong tac bao dung tai lieu."))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"cong tac mo dung tai lieu.\") OR (\"cong tac bao dung tai lieu.\"))".
• Removing quotes may allow a broader search: (( cong tac mo dung tai lieu. ) OR ( cong tac bao dung tai lieu. )).
• Adding a wildcard symbol may retrieve word variants: (("cong tac mo dung tai lieu.") OR ("cong tac bao dung tai lieu."))*.