Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
hoc sach » hoc sinh, hoc cac, hoc anh
nang ma » tang ma, sang ma, nang cao
qua dam » cua dam, qua da, dua dam
kinh ve » dinh ve, minh ve, kinh viet
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) or (hoc sach)) ky nang ma hoi. hieu qua dam tu va ((kinh ve) OR (kinh te)) su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) ky nang ma hoi. hieu qua dam tu va ((kinh ve) OR (kinh te)) su viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (hoc sach)) ky nang ma hoi. hieu qua dam tu va ((kinh ve) OR (kinh te)) su viet".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) ky nang ma hoi. hieu qua dam tu va ((kinh ve) OR (kinh te)) su viet*.