Perhaps you should try some spelling variations:
vien cap » vien cac, vien cao, vien canh
thanh va » thanh van, hanh va, thanh ha
va thanh » gia thanh, ban thanh, va tinh
vien can » vien canh, vien cac, vien cao
sach ky » sach y, sach ty, sach kem
lang xa » lang ha, dang xay, lang van
cua tre » cua te, cuu tre, cua triet
sac ky » cac ky, sai ky
va cua » va chua, via cua, ca cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu ((sach ky) or (sac ky)) lang xa hoi. hieu ((vien cap) OR (vien can)) nuoc va thanh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu ((sach ky) OR (sac ky)) lang xa hoi. hieu ((vien cap) OR (vien can)) nuoc va thanh va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu ((sach ky) or (sac ky)) lang xa hoi. hieu ((vien cap) OR (vien can)) nuoc va thanh va cua tre".
• Adding a wildcard symbol may retrieve word variants: vu ((sach ky) or (sac ky)) lang xa hoi. hieu ((vien cap) OR (vien can)) nuoc va thanh va cua tre*.