Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
duc van » duc va, duc tan, duc manh
ty hang » ty xang, thi hang, thu hang
hanh va » hang va, hanh vi
ly hang » ly quang
duc ban » duc tan, dua ban, duc man
va cua » va chua, via cua, ca cua
qua ca » qua cac, qua cua, qua cai
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: thu sach ((ty hang) or (ly hang)) cau hoi. hieu qua ca ((duc ban) OR (duc van)) hanh va cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ((ty hang) OR (ly hang)) cau hoi. hieu qua ca ((duc ban) OR (duc van)) hanh va cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ((ty hang) or (ly hang)) cau hoi. hieu qua ca ((duc ban) OR (duc van)) hanh va cua te".
• Adding a wildcard symbol may retrieve word variants: thu sach ((ty hang) or (ly hang)) cau hoi. hieu qua ca ((duc ban) OR (duc van)) hanh va cua te*.