Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
toc sach » hoc sach, doc sach, thuoc sach
hieu ve » hieu va, hieu van
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
cac tu » cac thu, cach tu, cac du
tu van » tu va
ve cac » va cac, vien cac
vi cu » vi su, vi xu
vi du » vi dum, va du, ve du

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) OR (toc sach)) ky lang xa hoi. hieu ve cac tu van hanh ((vi cu) or (vi du)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky lang xa hoi. hieu ve cac tu van hanh ((vi cu) OR (vi du)) tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ky lang xa hoi. hieu ve cac tu van hanh ((vi cu) or (vi du)) tren".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) ky lang xa hoi. hieu ve cac tu van hanh ((vi cu) or (vi du)) tren*.