Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hanh vai » hanh vi, hanh va, hanh tai
van hanh » van thanh, ban hanh, van anh
luc van » luoc van, luu van, duc van
la tren » loai tren, dua tren, dat tren
mai hoi » mai khoi, dai hoi, lai hoi
ky dang » ky nang, ky danh
ky sang » ky nang, ky tang, duy sang
ve cac » va cac, vien cac
vai la » tai la, vai va
ve cai » va cai, ve tai, ve cau

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ((ky sang) OR (ky dang)) mai hoi. hieu ((ve cai) or (ve cac)) luc van hanh vai la tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ((ky sang) OR (ky dang)) mai hoi. hieu ((ve cai) OR (ve cac)) luc van hanh vai la tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ((ky sang) OR (ky dang)) mai hoi. hieu ((ve cai) or (ve cac)) luc van hanh vai la tren".
• Adding a wildcard symbol may retrieve word variants: thu sach ((ky sang) OR (ky dang)) mai hoi. hieu ((ve cai) or (ve cac)) luc van hanh vai la tren*.