Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
hieu van » hieu va, thien van, lieu va
duoc ban » duc ban, quoc ban, buoc ban
hanh de » hanh ve, hanh kem
hanh di » hanh vi, hang di, danh di
da duoc » tao duoc, hoa duoc
cua tre » cua te, cuu tre, cua triet
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho tang
su sach » so sach, vu sach
van da » van dao, van dau, van dan

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) or (su sach)) ky tang xa hoi. hieu van da duoc ban ((hanh di) OR (hanh de)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thuoc sach) OR (su sach)) ky tang xa hoi. hieu van da duoc ban ((hanh di) OR (hanh de)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thuoc sach) or (su sach)) ky tang xa hoi. hieu van da duoc ban ((hanh di) OR (hanh de)) cua tre".
• Adding a wildcard symbol may retrieve word variants: ((thuoc sach) or (su sach)) ky tang xa hoi. hieu van da duoc ban ((hanh di) OR (hanh de)) cua tre*.