Perhaps you should try some spelling variations:
van cham » van chat, van tham, va cham
han thai » han tai, ban thai, van thai
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
thai va » thai van
luc va » duc va, tuc va
loc va » hoc va
thiet » thieu

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 y ((nang xa) OR (nang ma)) hoi. hieu van cham ((luc va) or (loc va)) han thai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((nang xa) OR (nang ma)) hoi. hieu van cham ((luc va) OR (loc va)) han thai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((nang xa) OR (nang ma)) hoi. hieu van cham ((luc va) or (loc va)) han thai va thiet".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((nang xa) OR (nang ma)) hoi. hieu van cham ((luc va) or (loc va)) han thai va thiet*.