Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
sach ty » sach y, sach tu, sach thu
van cac » van hac, van cau, van bac
ty nang » ky nang, ty xang, ty hang
tac xa » tuc xa
x hoi » xa hoi, o hoi, x ho
vi su » va su, ve su, oi su
ki su » ky 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 ty nang x hoi. hieu van cac ((tac xa) or (tac da)) thanh ((vi su) OR (ki su)) viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty nang x hoi. hieu van cac ((tac xa) OR (tac da)) thanh ((vi su) OR (ki su)) viet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty nang x hoi. hieu van cac ((tac xa) or (tac da)) thanh ((vi su) OR (ki su)) viet*".