Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
cao hoc » co hoc, cho hoc, chat hoc
luc van » luoc van, luu van, luc va
duc van » duc va, duc tan, duc manh
cua tre » cua te, cuu tre, cua triet
y nang » ly nang, v nang, may nang
anh vi » hanh vi, anh va, anh ve
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ((y nang) OR (ky nang)) cao hoc. hieu van nam ((luc van) or (duc van)) anh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((y nang) OR (ky nang)) cao hoc. hieu van nam ((luc van) OR (duc van)) anh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((y nang) OR (ky nang)) cao hoc. hieu van nam ((luc van) or (duc van)) anh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ((y nang) OR (ky nang)) cao hoc. hieu van nam ((luc van) or (duc van)) anh vi cua tre*.