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
cau tren » cu tren, dau tren, ca tren
hieu ve » hieu va, hieu van
cac cuc » cac cuoc, cac cua, cac nuoc
cuc ban » cua ban, cac ban, cuu ban
ky tang » ky nang, ky dang, kho tang
ky sang » ky nang, ky dang, duy sang
ma hoi » mai hoi, xa hoi, ma hoa
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) OR (ky tang)) ma hoi. hieu ve cac cuc ban ((thanh dat) or (hanh tai)) cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ((ky sang) OR (ky tang)) ma hoi. hieu ve cac cuc ban ((thanh dat) OR (hanh tai)) cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ((ky sang) OR (ky tang)) ma hoi. hieu ve cac cuc ban ((thanh dat) or (hanh tai)) cau tren".
• Adding a wildcard symbol may retrieve word variants: thu sach ((ky sang) OR (ky tang)) ma hoi. hieu ve cac cuc ban ((thanh dat) or (hanh tai)) cau tren*.