Perhaps you should try some spelling variations:
vien cac » vien bach, vien dai, vien da
thanh vi » hanh vi, thanh va, thanh ve
sach ky » sac ky, sach y, sach ty
su sach » so sach, vu sach
su viet » so viet
ve cac » va cac
tac xa » tuc xa
x hoi » xa hoi, o hoi, x ho
vi su » va su, ve su, ki su

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 ky nang x hoi. hieu ((ve cac) OR (vien cac)) ((tac xa) or (tac da)) thanh vi su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang x hoi. hieu ((ve cac) OR (vien cac)) ((tac xa) OR (tac da)) thanh vi su viet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang x hoi. hieu ((ve cac) OR (vien cac)) ((tac xa) or (tac da)) thanh vi su viet*".