Perhaps you should try some spelling variations:
ban xanh » ban hanh, ban anh, ban banh
quoc ban » quoc bao, quoc lan, quoc quan
cam quoc » cac quoc, cao quoc, nam quoc
sach ky » sac ky, sach y, sach ty
xanh di » danh di, vanh dai, xanh tai
hieu va » lieu va, hieu qua
ca tren » cau tren, cu tren, la tren
nang ho » nang hoc, nang co, tang ho
va cam » va cham, va cac, va cao
nang o » nang co, nang ro, nang x
di ca » di cau, di cua, doi ca

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