Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
va cham » va chat, va tham
hanh ve » hanh vi, hanh va, hanh kem
va hanh » van hanh, va thanh, va danh
vu cham » vu kham, tu cham, qua cham
thu sac » thu sach, thu san, thu xac
nang co » nang doc, nang noi, nang hoc
sac ky » cac ky, sai ky
luc va » duc va, tuc va, loc va
ve dau » va dau, ve du, ke dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sac ky ((nang co) OR (nang cao)) hoc. hieu ((va cham) or (vu cham)) luc va hanh ve dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sac ky ((nang co) OR (nang cao)) hoc. hieu ((va cham) OR (vu cham)) luc va hanh ve dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sac ky ((nang co) OR (nang cao)) hoc. hieu ((va cham) or (vu cham)) luc va hanh ve dau tren".
• Adding a wildcard symbol may retrieve word variants: thu sac ky ((nang co) OR (nang cao)) hoc. hieu ((va cham) or (vu cham)) luc va hanh ve dau tren*.