Perhaps you should try some spelling variations:
sach tien » sach tren, sach thieu
tien cao » vien cao, tien giao, thien cac
sach xat » sach dat, sach phat, sach dao
lao khoa » lo khoa, da khoa, ly khoa
khoa hoc » hoa hoc
tu sach » thu sach, su sach, te sach
cao kha » cao khai, cao khoa, co kha
kha hoc » nha hoc, kha hoa, khi hoc
sach xa » sach dao, sach nha, sach bai
xat lao » luat lao, suat lao
xa cao » va cao, ca cao

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 tien cao kha hoc ) or ((( tu sach xa cao kha hoc ) or ( tu sach xat lao khoa hoc ))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach tien cao kha hoc ) OR ((( tu sach xa cao kha hoc ) OR ( tu sach xat lao khoa hoc )))).
• Adding a wildcard symbol may retrieve word variants: (( tu sach tien cao kha hoc ) or ((( tu sach xa cao kha hoc ) or ( tu sach xat lao khoa hoc ))))*.