Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh tai » thanh tai, hang tai, han tai
hanh dai » hanh dao, vanh dai, thanh dat
ve pham » vi pham, v pham, ve phan
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, sang ma, nang cao
ma hoi » mai hoi, xa hoi, ma hoa
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 ma hoi. hieu ve pham duc va ((hanh dai) OR (hanh tai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) v nang ma hoi. hieu ve pham duc va ((hanh dai) OR (hanh tai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) v nang ma hoi. hieu ve pham duc va ((hanh dai) OR (hanh tai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) v nang ma hoi. hieu ve pham duc va ((hanh dai) OR (hanh tai)) cua tre*.