Perhaps you should try some spelling variations:
thien van » thi van
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, nang ma, mang xa
lang xa » lang ha, dang xay, lang van
nam hoc » nam moc, nam hoi, am hoc
va hang » van hang, va nang, va lang
doi cu » doi cua, doi ca, doi su
doi co » doi bo, moi co, hoi co

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 ky ((nang xa) or (lang xa)) hoi. thien van nam hoc va hang ((doi cu) OR (doi co)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang xa) OR (lang xa)) hoi. thien van nam hoc va hang ((doi cu) OR (doi co)) tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang xa) or (lang xa)) hoi. thien van nam hoc va hang ((doi cu) OR (doi co)) tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang xa) or (lang xa)) hoi. thien van nam hoc va hang ((doi cu) OR (doi co)) tren*.