Perhaps you should try some spelling variations:
luc ngan » luc nganh, luc nhan, luat ngan
tu sach » thu sach, su sach, te sach
hang vi » hang va, hang di, khang voi
cau luc » cau truc, cau phuc
sach ty » sach y, sach tu, sach thu
hieu ve » hieu va, hieu van
ca tren » cau tren, cu tren, la tren
ty nang » ky nang, ty xang, ty hang
ve cau » ke cau, va cau, ve cac
o hai » co hai, so hai, o lai
o hoi » co hoi, o hoc, o hoa

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 ty nang ((o hoi) OR (o hai)). hieu ve cau luc ngan ((hang vi) or (hanh vi)) ca tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang ((o hoi) OR (o hai)). hieu ve cau luc ngan ((hang vi) OR (hanh vi)) ca tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty nang ((o hoi) OR (o hai)). hieu ve cau luc ngan ((hang vi) or (hanh vi)) ca tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang ((o hoi) OR (o hai)). hieu ve cau luc ngan ((hang vi) or (hanh vi)) ca tren*.