Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nang dai » nang dau, nang tai, lang dai
tu sach » thu sach, su sach, te sach
dai hoi » dai hoc, dai hai, dai moi
hieu ve » hieu va, hieu van
cau duc » cao duc, cau luc, chu duc
va hanh » van hanh, va thanh, va danh
luu tre » luu tru, cuu tre, luy tre
y nang » ky nang, ly nang, v nang
vi luu » vi lua

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (toc sach)) y nang dai hoi. ((hieu ve) or (lieu va)) cau duc va hanh vi luu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (toc sach)) y nang dai hoi. ((hieu ve) OR (lieu va)) cau duc va hanh vi luu tre.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (toc sach)) y nang dai hoi. ((hieu ve) or (lieu va)) cau duc va hanh vi luu tre*.