Perhaps you should try some spelling variations:
quoc lan » quoc ban, nuoc luan, quoc quan
lan hanh » ban hanh, van hanh, lan anh
hanh tai » thanh tai, hang tai, han tai
te sach » toc sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
tai cua » thai cua, tai cuc, tri cua
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: te sach ky ((nang xa) or (nang ma)) hoi. hieu ((qua cac) OR (cua cac)) quoc lan hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky ((nang xa) OR (nang ma)) hoi. hieu ((qua cac) OR (cua cac)) quoc lan hanh tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky ((nang xa) or (nang ma)) hoi. hieu ((qua cac) OR (cua cac)) quoc lan hanh tai cua tre".
• Adding a wildcard symbol may retrieve word variants: te sach ky ((nang xa) or (nang ma)) hoi. hieu ((qua cac) OR (cua cac)) quoc lan hanh tai cua tre*.