Perhaps you should try some spelling variations:
hieu viet » sieu viet, hieu viec, lieu viet
viet sach » viet anh, dien sach, viet tech
sach nuoc » sach duoc, cac nuoc, bach tuoc
xanh tai » hanh tai, anh tai, vanh tai
nang mai » nang ma, nang tai, lang mai
xanh di » danh di, vanh dai
sach ky » sac ky, sach y, sach kem
mai hoi » mai khoi, dai hoi, lai hoi
sach ty » sach y, sach tu, sach thu
cua tre » cua te, cuu tre, cua triet

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

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach ky) or (sach ty)) nang mai hoi. hieu viet sach nuoc va ((xanh di) OR (xanh tai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sach ty)) nang mai hoi. hieu viet sach nuoc va ((xanh di) OR (xanh tai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ky) or (sach ty)) nang mai hoi. hieu viet sach nuoc va ((xanh di) OR (xanh tai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach ky) or (sach ty)) nang mai hoi. hieu viet sach nuoc va ((xanh di) OR (xanh tai)) cua tre*.