Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
nhan luc » nang luc
van hanh » van thanh, ban hanh, van anh
hanh de » hanh ve, hanh kem
nang ma » tang ma, sang ma, nang cao
cua tre » cuu tre, cua triet, dua tren
hau luc » hau loc, cau luc, hieu luc
sach ky » sac ky, sach y, sach ty
ma hoi » mai hoi, xa hoi, ma hoa
cua te » cua tu

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 ky nang ma hoi. hieu van ((hau luc) or (nhan luc)) van hanh de ((cua tre) OR (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang ma hoi. hieu van ((hau luc) OR (nhan luc)) van hanh de ((cua tre) OR (cua te)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky nang ma hoi. hieu van ((hau luc) or (nhan luc)) van hanh de ((cua tre) OR (cua te))".
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang ma hoi. hieu van ((hau luc) or (nhan luc)) van hanh de ((cua tre) OR (cua te))*.