Perhaps you should try some spelling variations:
thieu nien » thien nhien
cao khoa » bao khoa, cac khoa, cao kha
lao khoa » lo khoa, da khoa, ly khoa
nien cac » vien cac, dien cac, bien cac
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
cac hoc » cach hoc, cac hop, bac hoc
va nang » van nang, da nang, cam nang
via cua » gia cua, gian cua, giau cua
ca cua » co cua

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 nang ((cao khoa) OR (lao khoa)). thieu nien cac hoc va nang ((via cua) or (ca cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((cao khoa) OR (lao khoa)). thieu nien cac hoc va nang ((via cua) OR (ca cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang ((cao khoa) OR (lao khoa)). thieu nien cac hoc va nang ((via cua) or (ca cua)) tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((cao khoa) OR (lao khoa)). thieu nien cac hoc va nang ((via cua) or (ca cua)) tre*.