Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
cua viet » ca viet, hoa viet, cua vat
thanh va » thanh van, hanh va, thanh ha
duc ban » duc tan, duc van, dua ban
vu kham » vu khanh
tu sach » thu sach, su sach, te sach
ky dang » ky nang, ky danh
ky lang » ky nang, ky tang, tay lang
vu cham » va cham, tu cham, qua cham
ha hoi » hoa hoi, ha noi, xa hoi
va cua » va chua, via cua, ca cua

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 lang) or (ky dang)) ha hoi. hieu ((vu cham) OR (vu kham)) duc ban thanh va cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky lang) OR (ky dang)) ha hoi. hieu ((vu cham) OR (vu kham)) duc ban thanh va cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky lang) or (ky dang)) ha hoi. hieu ((vu cham) OR (vu kham)) duc ban thanh va cua viet".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky lang) or (ky dang)) ha hoi. hieu ((vu cham) OR (vu kham)) duc ban thanh va cua viet*.