Perhaps you should try some spelling variations:
trach nhiem » trac nghiem
nghiem quoc » nghiem nuoc, nghiep quoc, nghiem thuoc
nghiem duoc » nghiem thuoc, nghe duoc
thuoc sach » hoc sach, nuoc sach, thuat sach
sach tranh » canh tranh
can trach » can tranh, canh tranh, can khach
nhiem d » nghiem d, nghiem de, nhiem va
tu can » tu ban, tu cac, thu canh
d hoc » du hoc, ad hoc, de hoc

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: (( tu can trach nhiem d hoc ) OR ( thuoc sach tranh ((nghiem quoc) OR (nghiem duoc)) hoi ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu can trach nhiem d hoc ) or ( thuoc sach tranh ((nghiem quoc) OR (nghiem duoc)) hoi ))~".
• Adding a wildcard symbol may retrieve word variants: (( tu can trach nhiem d hoc ) or ( thuoc sach tranh ((nghiem quoc) OR (nghiem duoc)) hoi ))*.