Perhaps you should try some spelling variations:
thien van » thi van
lang van » dang van, tang van, hoang van
hang vi » hang va, hanh vi, khang voi
hang di » hang doi, hang dien, hang dich
nam hoc » nam moc, nam hoi, am hoc
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
cu tren » tu tren, dua tren

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