Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
nang hoc » nang luc, dong hoc, hang hoa
nang doc » nang luc
cac sau » cac san, ca sau, cac mau
hieu ve » hieu va, hieu van
tu sach » thu sach, su sach, tu cach
te sach » toc sach
ve cac » va cac, vien cac
sau va » su va, dau va, lau va
va dao » ca dao
dao vi » dao voi, dao ve, dao va
vi cau » va cau, ve cau, di cau

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (te sach)) ly ((nang hoc) OR (nang doc)) hoi. hieu ve cac sau va dao vi cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (te sach)) ly ((nang hoc) OR (nang doc)) hoi. hieu ve cac sau va dao vi cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (te sach)) ly ((nang hoc) OR (nang doc)) hoi. hieu ve cac sau va dao vi cau tren".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (te sach)) ly ((nang hoc) OR (nang doc)) hoi. hieu ve cac sau va dao vi cau tren*.