Perhaps you should try some spelling variations:
nang doc » nang luc
cu tren » tu tren, dua tren
cam luc » cam xuc, cau luc
nang co » nang cao, nang noi, nang hoc
hieu ve » hieu va, hieu van
va dau » va dao
va dan » ca dan, va dao, va dap
tu sac » tu sach, tu cac, tu san
sac ky » cac ky, sai ky
ve cam » ve cham, ve cac, va cam
ca cu » ca cua, cua cu, ca 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 sac ky ((nang co) or (nang doc)) hoi. hieu ve cam luc ((va dan) OR (va dau)) ca cu tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky ((nang co) OR (nang doc)) hoi. hieu ve cam luc ((va dan) OR (va dau)) ca cu tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky ((nang co) or (nang doc)) hoi. hieu ve cam luc ((va dan) OR (va dau)) ca cu tren".
• Adding a wildcard symbol may retrieve word variants: tu sac ky ((nang co) or (nang doc)) hoi. hieu ve cam luc ((va dan) OR (va dau)) ca cu tren*.