Perhaps you should try some spelling variations:
duc tien » duc thien, luc tieng, thuc tien
xa thanh » va thanh, ha thanh, ta thanh
sach ky » sac ky, sach y, sach ty
duc tre » duoc tren
tu sach » thu sach, su sach, te sach
cac toc » cac toi, cac nuoc, cac thoi
hieu ve » hieu va, hieu van
dang ma » dang mau, dang mam, dang mat
ky dang » ky nang, ky danh
xa hanh » xa khanh, va hanh, da hanh
ve cac » va cac, vien cac

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 dang ma hoa. hieu ve cac toc ((xa hanh) OR (xa thanh)) may ((duc tre) or (duc tien))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky dang ma hoa. hieu ve cac toc ((xa hanh) OR (xa thanh)) may ((duc tre) OR (duc tien)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky dang ma hoa. hieu ve cac toc ((xa hanh) OR (xa thanh)) may ((duc tre) or (duc tien))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky dang ma hoa. hieu ve cac toc ((xa hanh) OR (xa thanh)) may ((duc tre) or (duc tien))*.