Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va
va dinh » van dinh, va kinh, va tinh
dinh va » dinh van, dinh ve, tinh va
su viet » so viet
ma hoi » mai hoi, xa hoi, ma hoa
dam tu » nam tu, cam tu, tam tu

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 ky nang ma hoi. ((hieu va) OR (hieu qua)) dam tu va dinh va su viet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky nang ma hoi. ((hieu va) OR (hieu qua)) dam tu va dinh va su viet".
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang ma hoi. ((hieu va) OR (hieu qua)) dam tu va dinh va su viet*.