Perhaps you should try some spelling variations:
sach tinh » sach kinh, sac tinh, sach tranh
sach tien » sach tren, sach thieu
tien lao » tien lam, kien lao, vien lao
lao khoa » lo khoa, da khoa, tai khoa
khoa hoc » hoa hoc
tinh lao » dinh lam, tinh nam, tinh va
su sach » so sach
te sach » toc sach
lao khi » cao khai, tao khoi, lao chai
khi hoc » khi hoi, khien hoc, thai hoc
vu sach » vu bach, vu khach
sach xa » sach dao, sach nha, sach bai
xa ly » xu ly, xa la, va ly

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

• Performing a fuzzy search may retrieve terms with similar spellings: (((( su sach tien lao khoa hoc ) or ( te sach tinh lao khi hoc ))) or ( vu sach xa ly khoa hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((( su sach tien lao khoa hoc ) OR ( te sach tinh lao khi hoc ))) OR ( vu sach xa ly khoa hoc )).
• Adding a wildcard symbol may retrieve word variants: (((( su sach tien lao khoa hoc ) or ( te sach tinh lao khi hoc ))) or ( vu sach xa ly khoa hoc ))*.