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

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