Perhaps you should try some spelling variations:
nang mai » nang tai, lang mai, nang cai
su sach » so sach, vu sach
hanh ky » hanh kem
xuc van » duc van, luc van, vuc van
sach vu » sach va, sach tu, sach uu
hieu va » lieu va, hieu qua
nang ma » tang ma, sang ma, nang cao
su viet » so viet
va cam » va cham, va cac, va cao

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach vu ((nang mai) OR (nang ma)) hoi. hieu va cam xuc van ((hanh ky) or (hanh vi)) su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach vu ((nang mai) OR (nang ma)) hoi. hieu va cam xuc van ((hanh ky) OR (hanh vi)) su viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach vu ((nang mai) OR (nang ma)) hoi. hieu va cam xuc van ((hanh ky) or (hanh vi)) su viet".
• Adding a wildcard symbol may retrieve word variants: su sach vu ((nang mai) OR (nang ma)) hoi. hieu va cam xuc van ((hanh ky) or (hanh vi)) su viet*.