Perhaps you should try some spelling variations:
trinh tu » trinh ky
trinh ca » trinh cau, trinh cua, trinh cac
trinh do » trinh ky
cac cac » cac cach, ca cac, cac bac
so viet » hoc viet
cac cay » ca cay, cac cam, cac cap
ca dan » cac dan, ca dao
dan va » doan va, dan ca, ban va
cac co » cac cong
cay co » tay co, cay cong

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (( cong trinh ca dan va cac cac co so viet nam ) or ( cong ((trinh tu) OR (trinh do)) dan va cac cay co so viet nam ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( cong trinh ca dan va cac cac co so viet nam ) OR ( cong ((trinh tu) OR (trinh do)) dan va cac cay co so viet nam )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( cong trinh ca dan va cac cac co so viet nam ) or ( cong ((trinh tu) OR (trinh do)) dan va cac cay co so viet nam ))".
• Adding a wildcard symbol may retrieve word variants: (( cong trinh ca dan va cac cac co so viet nam ) or ( cong ((trinh tu) OR (trinh do)) dan va cac cay co so viet nam ))*.