Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh dai » hanh tai, hanh dao, vanh dai
nang mai » nang ma, nang tai, lang mai
ve pham » vi pham, v pham, ve phan
han tai » hang tai, nhan tai, van tai
hieu ve » hieu va, hieu van
mai hoi » mai khoi, dai hoi, lai hoi
cua tre » cua te, cuu tre, cua triet
v nang » va nang, vu nang, van nang

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) or (toc sach)) v nang mai hoi. hieu ve pham duc va ((hanh dai) or (han tai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) v nang mai hoi. hieu ve pham duc va ((hanh dai) OR (han tai)) cua tre.
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) v nang mai hoi. hieu ve pham duc va ((hanh dai) or (han tai)) cua tre*.