Perhaps you should try some spelling variations:
thien van » thi van
hoc sach » hoc sinh, hoc cac, hoc anh
kho tang » cao tang
cau tren » cu tren, dau tren, ca tren
hieu ve » hieu va, hieu van
ky tang » ky nang, ky dang, ky trong
cam duc » cam xuc, cao duc, pham duc
va dan » ca dan, va dao, va dau
dan di » danh di, dan da, dan de
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: hoc sach ((ky tang) OR (kho tang)) xa hoi. ((hieu ve) or (thien van)) cam duc va dan di cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ((ky tang) OR (kho tang)) xa hoi. ((hieu ve) OR (thien van)) cam duc va dan di cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ((ky tang) OR (kho tang)) xa hoi. ((hieu ve) or (thien van)) cam duc va dan di cau tren".
• Adding a wildcard symbol may retrieve word variants: hoc sach ((ky tang) OR (kho tang)) xa hoi. ((hieu ve) or (thien van)) cam duc va dan di cau tren*.