Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
cua viet » ca viet, hoa viet, cua vat
thanh di » thanh doi, thanh de, thanh do
nam thuc » nam thuoc, am thuc, nam thu
cam thuc » am thuc, cam thu, can thuc
hieu van » hieu va, thien van, lieu va
thu sach » tu sach, thuat sach, thuoc sach
sang ma » tang ma, nang ma, sang tao
ky sang » ky nang, ky dang, ky tang
te sach » toc sach
ma hoi » mai hoi, xa hoi, ma hoa
di cua » dai cua, doi cua, de cua

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 (thu sach)) ky sang ma hoi. hieu van ((cam thuc) OR (nam thuc)) van thanh di cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (thu sach)) ky sang ma hoi. hieu van ((cam thuc) OR (nam thuc)) van thanh di cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (thu sach)) ky sang ma hoi. hieu van ((cam thuc) OR (nam thuc)) van thanh di cua viet".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (thu sach)) ky sang ma hoi. hieu van ((cam thuc) OR (nam thuc)) van thanh di cua viet*.