Perhaps you should try some spelling variations:
ban hanh » ban hang
cau tren » cu tren, dau tren, ca tren
sach ky » sach y, sach ty, sach kem
hieu va » lieu va, hieu qua
cam duc » cam xuc, cao duc, pham duc
duc ban » duc tan, duc van, dua ban
hanh di » hanh vi, hanh de, hang di
sac ky » cac ky, sai ky
nang o » nang co, nang ho, nang ro
va cam » va cham, va cac, va cao
di cau » da cau, diem cau
o hoc » co hoc, mo hoc, so hoc

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 ky) or (sac ky)) nang o hoc. hieu va cam duc ban hanh di cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sac ky)) nang o hoc. hieu va cam duc ban hanh di cau tren.
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sac ky)) nang o hoc. hieu va cam duc ban hanh di cau tren*.