Perhaps you should try some spelling variations:
dung sai » dung tai, dung va, dung dat
su sach » so sach, vu sach
sai cua » dai cua, hai cua, lai cua
thu xac » thau xay
sach ty » sach y, sach tu, sach thu
cua tre » cua te, cuu tre, cua triet
hieu he » hieu ve, hiem he, hieu le
cho hoc » co hoc, khoa hoc
cao hoc » co hoc, chat hoc
ty nang » ky nang, ty xang, ty hang
thu xa » thu ha, thu xe, thu ba
he nam » ha nam, nghe nam

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 ty nang ((cao hoc) OR (cho hoc)). hieu he nam ((thu xa) or (thu xac)) dung sai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty nang ((cao hoc) OR (cho hoc)). hieu he nam ((thu xa) OR (thu xac)) dung sai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty nang ((cao hoc) OR (cho hoc)). hieu he nam ((thu xa) or (thu xac)) dung sai cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ty nang ((cao hoc) OR (cho hoc)). hieu he nam ((thu xa) or (thu xac)) dung sai cua tre*.