Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang xa » lang xa, nang ma, mang xa
hieu ve » hieu va, hieu van
duc van » duc va, duc manh, duc phan
so viet » hoc viet
ve cam » ve cham, ve cac, va cam
vi so » vi soi, vi mo, va so

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky ((nang xa) or (nang x)) hoi. hieu ve cam ((duc van) OR (duc tan)) hanh vi so viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang xa) OR (nang x)) hoi. hieu ve cam ((duc van) OR (duc tan)) hanh vi so viet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang xa) or (nang x)) hoi. hieu ve cam ((duc van) OR (duc tan)) hanh vi so viet*".