Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
nang cho » nang chon, ngang cho, nang cao
hieu van » thien van, lieu va, hieu ve
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
cac vuc » cac vung, cac cuoc, cac quoc
hieu va » lieu va, hieu qua
sach ty » sach y, sach tu, sach thu
cho hoc » co hoc, khoa hoc
ty nang » ky nang, ty xang, ty hang
cua cau » cua cac, cua chu, cua cay
vi cua » vai cua, di cua

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 ty nang cho hoc. ((hieu van) OR (hieu va)) ((cac vuc) or (cac nuoc)) van hanh vi cua cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ty nang cho hoc. ((hieu van) OR (hieu va)) ((cac vuc) OR (cac nuoc)) van hanh vi cua cau*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ty nang cho hoc. ((hieu van) OR (hieu va)) ((cac vuc) or (cac nuoc)) van hanh vi cua cau*".