Perhaps you should try some spelling variations:
trai nghiep » trai nghiem, trac nghiem, mai nghiep
sach trach » sach tranh, sat trach
khach trai » khac trai, khanh tra, kham trai
sach truc » cach thuc, sach tren, sach thu
nghiep vu » nghiep va
tu khach » vu khach, tu hach, cua khach
nhiem d » nghiem d, nghiem de, nghiem do
vu hoc » tu hoc, va hoc, du hoc
d hoc » du hoc, ad hoc, de hoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tu ((sach trach) OR (sach truc)) nhiem d hoc ) or ( tu khach trai nghiep vu hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu ((sach trach) OR (sach truc)) nhiem d hoc ) OR ( tu khach trai nghiep vu hoc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu ((sach trach) OR (sach truc)) nhiem d hoc ) or ( tu khach trai nghiep vu hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( tu ((sach trach) OR (sach truc)) nhiem d hoc ) or ( tu khach trai nghiep vu hoc ))*.