Perhaps you should try some spelling variations:
van doanh » toan doanh, van dong, van thanh
thu sach » thuat sach, thuoc sach, thu hoach
tu sach » su sach, te sach, tu cach
tai cua » thai cua, tai cuc, tri cua
choi xu » choi tu, chi xu, choi au
ve choi » ve thoi, ve cho, ve khoi
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, sang ma, nang cao
xu van » tu van, vu van, su van

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 (thu sach)) ty ((nang ma) or (nang x)) hoi. hieu ve choi xu van doanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ty ((nang ma) OR (nang x)) hoi. hieu ve choi xu van doanh tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (thu sach)) ty ((nang ma) or (nang x)) hoi. hieu ve choi xu van doanh tai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (thu sach)) ty ((nang ma) or (nang x)) hoi. hieu ve choi xu van doanh tai cua tre*.