Perhaps you should try some spelling variations:
tranh nhiem » trach nhiem, trinh nhiet
sach tranh » canh tranh
sach trien » sach tien, sach thieu, cach thien
sach tren » sach tien
nhiem te » nghiem te, nhiem ve, nghiem de
nghiep o » nghiep so, nghiep co, nghiep y
te sach » toc sach
o hoc » co hoc, mo hoc, so hoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( te sach tranh nhiem te hoc ) or ( nuoc ((sach trien) or (sach tren)) nghiep o hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( te sach tranh nhiem te hoc ) OR ( nuoc ((sach trien) OR (sach tren)) nghiep o hoc )).
• Adding a wildcard symbol may retrieve word variants: (( te sach tranh nhiem te hoc ) or ( nuoc ((sach trien) or (sach tren)) nghiep o hoc ))*.