Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
van hanh » van thanh, ban hanh, van anh
ty hang » ly hang, thi hang, thu hang
tu sach » thu sach, su sach, te sach
duc van » duc va, duc tan, duc manh
hanh va » hang va, hanh vi
qua ca » qua cac, qua cua, qua cai
ca duc » cao duc, cua duc, ca dua
va cua » va chua, via cua, ca cua
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((thuoc sach) or (tu sach)) ((ty hang) OR (ty xang)) cau hoi. hieu qua ca duc van hanh va cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thuoc sach) OR (tu sach)) ((ty hang) OR (ty xang)) cau hoi. hieu qua ca duc van hanh va cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thuoc sach) or (tu sach)) ((ty hang) OR (ty xang)) cau hoi. hieu qua ca duc van hanh va cua te".
• Adding a wildcard symbol may retrieve word variants: ((thuoc sach) or (tu sach)) ((ty hang) OR (ty xang)) cau hoi. hieu qua ca duc van hanh va cua te*.