Perhaps you should try some spelling variations:
thanh phai » thanh hai, thanh phan, thanh pham
van thanh » ban thanh, van tuan
thu sach » tu sach, thuat sach, thuoc sach
sach ky » sac ky, sach y, sach ty
phai la » phai lam, phan lap, phan lan
luc van » luoc van, luu van, duc van
la tren » loai tren, dua tren, dat tren
dai hoi » dai hoc, dai hai, dai moi
mai hoi » mai khoi, lai hoi, mai doi
ky lang » ky nang, ky dang, ky tang
ve cac » va cac, vien cac
ve cau » ke cau, va cau, le cau

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 ky lang ((mai hoi) OR (dai hoi)). hieu ((ve cau) or (ve cac)) luc van thanh phai la tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky lang ((mai hoi) OR (dai hoi)). hieu ((ve cau) OR (ve cac)) luc van thanh phai la tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky lang ((mai hoi) OR (dai hoi)). hieu ((ve cau) or (ve cac)) luc van thanh phai la tren".
• Adding a wildcard symbol may retrieve word variants: thu sach ky lang ((mai hoi) OR (dai hoi)). hieu ((ve cau) or (ve cac)) luc van thanh phai la tren*.