Perhaps you should try some spelling variations:
cham thuc » nham thuc, pham thuc, tham thuc
nham thu » nham thuc, nam thu, pham thu
te sach » toc sach
sach ky » sac ky, sach y, sach ty
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
hieu ve » hieu va, hieu van
su hien » su kien, su tien, thu hien
va dat » va dao, va dau, va dap
dat vi » dat va, hat vi, dat ve
vi su » va su, ve su, ki su

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 ky lang xa hoi. hieu ve ((cham thuc) or (nham thu)) va dat vi su hien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky lang xa hoi. hieu ve ((cham thuc) OR (nham thu)) va dat vi su hien.
• Adding a wildcard symbol may retrieve word variants: te sach ky lang xa hoi. hieu ve ((cham thuc) or (nham thu)) va dat vi su hien*.