Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
cau tren » cu tren, dau tren, ca tren
sach ky » sac ky, sach y, sach ty
nang xa » nang x, nang ma, mang xa
lang xa » lang ha, dang xay, lang van
hieu ve » hieu va, hieu van
ve khac » vu khac, de khac, se khac
phuc va » thuc va, chuc va, thuc vat
danh va » doanh va, hanh va, anh va
va cau » van cau, va cac, va dau

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 ((nang xa) or (lang xa)) hoi. hieu ve khac ((phuc va) OR (phuc vu)) danh va cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ky ((nang xa) OR (lang xa)) hoi. hieu ve khac ((phuc va) OR (phuc vu)) danh va cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ky ((nang xa) or (lang xa)) hoi. hieu ve khac ((phuc va) OR (phuc vu)) danh va cau tren".
• Adding a wildcard symbol may retrieve word variants: hoc sach ky ((nang xa) or (lang xa)) hoi. hieu ve khac ((phuc va) OR (phuc vu)) danh va cau tren*.