Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
thanh va » thanh van, hanh va, thanh ha
su sach » so sach, vu sach
ty nang » ky nang, ty xang, ty hang
duc ban » duc tan, duc van, dua ban
sach ty » sach y, sach tu, sach thu
va cao » va cac, va co, va dao
va cua » va chua, via cua, ca cua
ve cam » ve cham, ve cac, va cam
cua te » cua tu
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: su sach ty nang ((o hoi) OR (o hai)). hieu ((ve cam) or (va cao)) duc ban thanh va cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty nang ((o hoi) OR (o hai)). hieu ((ve cam) OR (va cao)) duc ban thanh va cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty nang ((o hoi) OR (o hai)). hieu ((ve cam) or (va cao)) duc ban thanh va cua te".
• Adding a wildcard symbol may retrieve word variants: su sach ty nang ((o hoi) OR (o hai)). hieu ((ve cam) or (va cao)) duc ban thanh va cua te*.