Perhaps you should try some spelling variations:
"sach tranh viet nam." » "sach thanh viet nam." (Expand Search), "canh tranh viet nam." (Expand Search), "sach trong viet nam." (Expand Search), "sach trang viet nam." (Expand Search), "sach thanh vien nam." (Expand Search), "sach trangh viet nam." (Expand Search), "sach trah viet nam." (Expand Search), "sach tanh viet nam." (Expand Search)
"sach tran viet nam." » "sach trang viet nam." (Expand Search), "sach tra viet nam." (Expand Search), "sach tan viet nam." (Expand Search), "sach san viet nam." (Expand Search), "sach gian viet nam." (Expand Search), "sach van viet nam." (Expand Search)
"sach anh viet nam." » "sach van viet nam." (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: (("sach tran viet nam.") OR ((("sach tranh viet nam.") OR ("sach anh viet nam."))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"sach tran viet nam.\") OR (((\"sach tranh viet nam.\") OR (\"sach anh viet nam.\"))))".
• Removing quotes may allow a broader search: (( sach tran viet nam. ) OR ((( sach tranh viet nam. ) OR ( sach anh viet nam. )))).
• Adding a wildcard symbol may retrieve word variants: (("sach tran viet nam.") OR ((("sach tranh viet nam.") OR ("sach anh viet nam."))))*.