Perhaps you should try some spelling variations:
cham hoc » cham soc, chat hoc, cham hoi
nang tai » tang tai, sang tai, nang cao
hang tai » hang va, dung tai
ban hanh » ban hang
vu sach » vu bach, su sach, vu khach
vai cua » hai cua, lai cua, bai cua
hoc ban » hoc bang, hoc dan, hoc bai
hieu va » lieu va, hieu qua
va cham » va chat, va tham
sach ky » sac ky, sach y, sach ty

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach ky ((nang tai) or (hang tai)) roi. hieu va cham hoc ban hanh ((vai cua) or (dai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ky ((nang tai) OR (hang tai)) roi. hieu va cham hoc ban hanh ((vai cua) OR (dai cua)) tre.
• Adding a wildcard symbol may retrieve word variants: vu sach ky ((nang tai) or (hang tai)) roi. hieu va cham hoc ban hanh ((vai cua) or (dai cua)) tre*.