Perhaps you should try some spelling variations:
thanh dat » thanh san, thanh hai, thanh van
thu sach » tu sach, thuat sach, thuoc sach
hanh tai » thanh tai, hang tai, han tai
dau tren » dau tien, dat tren, dau tieng
hieu ve » hieu va, hieu van
sach ky » sac ky, sach y, sach ty
cac cuc » cac cuoc, cac cua, cac nuoc
cuc ban » cua ban, cac ban, cuu ban
ky sang » ky nang, ky dang, ky tang
ma hoi » mai hoi, ma hoa, me hoi
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: thu sach ky sang ((ma hoi) OR (xa hoi)). hieu ve cac cuc ban ((thanh dat) or (hanh tai)) dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky sang ((ma hoi) OR (xa hoi)). hieu ve cac cuc ban ((thanh dat) OR (hanh tai)) dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky sang ((ma hoi) OR (xa hoi)). hieu ve cac cuc ban ((thanh dat) or (hanh tai)) dau tren".
• Adding a wildcard symbol may retrieve word variants: thu sach ky sang ((ma hoi) OR (xa hoi)). hieu ve cac cuc ban ((thanh dat) or (hanh tai)) dau tren*.