Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
cac khoi » cac thoi, cach thoi, hoc khoi
hanh vai » hanh vi, hanh tai, hanh van
sach ky » sac ky, sach y, sach ty
hanh va » hang va, hanh vi
tu sach » thu sach, su sach, te sach
ky sang » ky nang, ky dang, ky tang
hieu ve » hieu va, hieu van
ve cham » va cham, ve chat, vu cham
soc va » hoc va, loc va, doc va

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 ky sang ((cac khoi) OR (cac khoan)). hieu ve cham soc va ((hanh vai) or (hanh va)) dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky sang ((cac khoi) OR (cac khoan)). hieu ve cham soc va ((hanh vai) OR (hanh va)) dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky sang ((cac khoi) OR (cac khoan)). hieu ve cham soc va ((hanh vai) or (hanh va)) dau tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ky sang ((cac khoi) OR (cac khoan)). hieu ve cham soc va ((hanh vai) or (hanh va)) dau tren*.