Perhaps you should try some spelling variations:
nghien duoc » nghiem duoc, nghe duoc, nghia duoc
dao nghien » dau nghien, vao nghien, cao nghien
thuoc sach » hoc sach, nuoc sach, thuat sach
sach truc » cach thuc, sach tren, sach thu
truc hiem » thuc hien, thuc hieu, truc tiep
sach dao » lanh dao
duoc hoc » quoc hoi
te sach » toc sach

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (( te sach dao nghien duoc hoc ) OR ( thuoc sach truc hiem ((tu hoc) OR (te hoc)) ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( te sach dao nghien duoc hoc ) or ( thuoc sach truc hiem ((tu hoc) OR (te hoc)) ))~".
• Adding a wildcard symbol may retrieve word variants: (( te sach dao nghien duoc hoc ) or ( thuoc sach truc hiem ((tu hoc) OR (te hoc)) ))*.