Perhaps you should try some spelling variations:
thanh hai » thanh phan, thanh hoa, thanh san
thanh dai » thanh tai, thanh dat, thanh oai
toc sach » hoc sach, thuoc sach, nuoc sach
hieu van » hieu va, thien van, lieu va
nam truc » nam truoc, nam thuc, nam trung
doc sach » hoc sach, nuoc sach, dac sac
nang ma » tang ma, sang ma, nang cao
truc va » thuc va, thuc vat, trung va
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa
y nang » ky nang, ly nang, v nang

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) or (doc sach)) y nang ma hoi. hieu van nam truc va ((thanh dai) OR (thanh hai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) y nang ma hoi. hieu van nam truc va ((thanh dai) OR (thanh hai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (doc sach)) y nang ma hoi. hieu van nam truc va ((thanh dai) OR (thanh hai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (doc sach)) y nang ma hoi. hieu van nam truc va ((thanh dai) OR (thanh hai)) cua tre*.