Perhaps you should try some spelling variations:
trien khai » trien nha
sach trien » sach tien, sach tren, sach thieu
khai khoa » thai khoa, chai khoa, khat khoa
chai hoa » chai khoa, chat hoa, cai hoa
te sach » toc sach
sach ha » sach nha, sach han, sach xa
ha chai » ha chau, va chai, hoa chat
tu sach » thu sach, su sach, tu cach

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 ha chai hoa hoc ) or ( tu sach trien khai khoa hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( te sach ha chai hoa hoc ) OR ( tu sach trien khai khoa hoc )).
• Adding a wildcard symbol may retrieve word variants: (( te sach ha chai hoa hoc ) or ( tu sach trien khai khoa hoc ))*.