Perhaps you should try some spelling variations:
toan tai » toan tap, doanh tai, toan ban
sach thu » sach thue, sach thieu, sach tham
va cham » va chat, va tham
va toan » van toan, bai toan, tap toan
truc va » thuc va, thuc vat, trung va
ve cham » ve chat, vu cham, ve chim
sach ty » sach y, sach tu, xach tay
nang xa » nang x, lang xa, nang ma
tai va » thai va, mai va, tri 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: so ((sach ty) OR (sach thu)) nang xa hoi. hieu ((ve cham) or (va cham)) truc va toan tai va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach ty) OR (sach thu)) nang xa hoi. hieu ((ve cham) OR (va cham)) truc va toan tai va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((sach ty) OR (sach thu)) nang xa hoi. hieu ((ve cham) or (va cham)) truc va toan tai va thiet".
• Adding a wildcard symbol may retrieve word variants: so ((sach ty) OR (sach thu)) nang xa hoi. hieu ((ve cham) or (va cham)) truc va toan tai va thiet*.