Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
hoc giao » hoc cao
thanh di » thanh doi, thanh de, thanh do
sach ky » sac ky, sach y, sach ty
hoc gia » hoc giai, toc gia, quoc gia
hieu ve » hieu va, hieu van
nang xa » nang x, lang xa, nang ma
so sach » so sanh, bo sach, co sach
di cau » da cau, diem cau

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky nang xa hoi. ((hieu ve) or (lieu va)) cham ((hoc gia) OR (hoc giao)) thanh di cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky nang xa hoi. ((hieu ve) OR (lieu va)) cham ((hoc gia) OR (hoc giao)) thanh di cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky nang xa hoi. ((hieu ve) or (lieu va)) cham ((hoc gia) OR (hoc giao)) thanh di cau tren".
• Adding a wildcard symbol may retrieve word variants: so sach ky nang xa hoi. ((hieu ve) or (lieu va)) cham ((hoc gia) OR (hoc giao)) thanh di cau tren*.