Perhaps you should try some spelling variations:
"sach viet khanh." » "sach viet thanh." (Expand Search), "sach viet khoang." (Expand Search), "sach viet anh." (Expand Search), "lich viet khanh." (Expand Search)
"sach viet khao." » "lich viet khao." (Expand Search), "sach viet ha." (Expand Search), "sach viet cho." (Expand Search), "sach viet phap." (Expand Search)
"sach viet giao." » "lich viet giao." (Expand Search)
"anh viet khao." » "anh viet ha." (Expand Search), "anh viet cho." (Expand Search), "anh viet phap." (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 viet khao.") OR ("sach viet giao."))) OR ("sach viet khanh."))) OR ("anh viet khao."))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((((\"sach viet khao.\") OR (\"sach viet giao.\"))) OR (\"sach viet khanh.\"))) OR (\"anh viet khao.\"))".
• Removing quotes may allow a broader search: (((((( sach viet khao. ) OR ( sach viet giao. ))) OR ( sach viet khanh. ))) OR ( anh viet khao. )).
• Adding a wildcard symbol may retrieve word variants: (((((("sach viet khao.") OR ("sach viet giao."))) OR ("sach viet khanh."))) OR ("anh viet khao."))*.