Perhaps you should try some spelling variations:
thien van » thi van
dang xay » dang van, van xay
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
nam hoc » nam moc, nam hoi, am hoc
va hang » van hang, va nang, va lang
hang di » hang doi, hang vi, hang dien
cu tren » tu tren, dua tren
di cu » di cau, di cua, di du

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 (dang xay)) hoi. thien van nam hoc va hang di cu tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang xa) OR (dang xay)) hoi. thien van nam hoc va hang di cu tren.
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang xa) or (dang xay)) hoi. thien van nam hoc va hang di cu tren*.