Perhaps you should try some spelling variations:
trinh ca » trinh cau, trinh cua, trinh cac
trinh tu » trinh ky, trinh do
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
cam co » nam co, lam co, cam lo
cac co » cac cong
tu dan » tuc dan, tu ban, cu dan
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 ((cam co) OR (cac co)) so viet nam ) or ( cong trinh tu 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 ((cam co) OR (cac co)) so viet nam ) OR ( cong trinh tu 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 ((cam co) OR (cac co)) so viet nam ) or ( cong trinh tu dan va cac cay co so viet nam ))".
• Adding a wildcard symbol may retrieve word variants: (( cong trinh ca dan va cac ((cam co) OR (cac co)) so viet nam ) or ( cong trinh tu dan va cac cay co so viet nam ))*.