Perhaps you should try some spelling variations:
thanh tuan » thanh toan, thanh xuan, thanh thanh
van thanh » ban thanh, van tuan
thu sach » tu sach, thuat sach, thuoc sach
dau tren » dau tien, dat tren, dau tieng
sach ty » sach y, sach tu, sach thu
luc van » luoc van, luu van, duc van
cac luc » cau luc, coc luc, cac nuoc
la tren » loai tren, dua tren, dat tren
ty nang » ky nang, ty xang, ty hang
hieu ve » hieu va, hieu van
ve cac » va cac, vien cac
o hai » co hai, so hai, o lai
o hoa » do hoa, so hoa, o ha

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 nang ((o hoa) or (o hai)). hieu ve cac luc van thanh tuan ((dau tren) or (la tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ty nang ((o hoa) OR (o hai)). hieu ve cac luc van thanh tuan ((dau tren) OR (la tren)).
• Adding a wildcard symbol may retrieve word variants: thu sach ty nang ((o hoa) or (o hai)). hieu ve cac luc van thanh tuan ((dau tren) or (la tren))*.