Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
sach duoc » sach nuoc, sach dao, sach dung
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
van dang » van dong, van dung, van nang
dang hai » dang khai, hang hai, dung hai
thi van » thi lan, thi hanh, thi nang
sach ky » sac ky, sach y, sach ty
hai cua » thai cua, dai cua, hoi cua
cua tre » cua te, cuu tre, cua triet
x hoi » xa hoi, x ho, 5 hoi
o hoi » co hoi, o hoc, o hai

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thuoc sach ky nang ((x hoi) OR (o hoi)). thi van ((sach duoc) or (cac nuoc)) van dang hai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuoc sach ky nang ((x hoi) OR (o hoi)). thi van ((sach duoc) OR (cac nuoc)) van dang hai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuoc sach ky nang ((x hoi) OR (o hoi)). thi van ((sach duoc) or (cac nuoc)) van dang hai cua tre".
• Adding a wildcard symbol may retrieve word variants: thuoc sach ky nang ((x hoi) OR (o hoi)). thi van ((sach duoc) or (cac nuoc)) van dang hai cua tre*.