Perhaps you should try some spelling variations:
"cong tac bao duong tai lieu." » "cong tac ba duong tai lieu." (Expand Search), "cong tac bao dong tai lieu." (Expand Search), "cong tac ban duong tai lieu." (Expand Search), "cong tac bao duong thai lieu." (Expand Search), "cong tac bao duong dai lieu." (Expand Search), "cong tac bao duong thi lieu." (Expand Search), "dong tac bao duong tai lieu." (Expand Search)
"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)

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 duong 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 duong tai lieu.\"))".
• Removing quotes may allow a broader search: (( cong tac mo dung tai lieu. ) OR ( cong tac bao duong tai lieu. )).
• Adding a wildcard symbol may retrieve word variants: (("cong tac mo dung tai lieu.") OR ("cong tac bao duong tai lieu."))*.