Perhaps you should try some spelling variations:
sach tham » sach nha
hieu van » hieu va, thien van, lieu va
sach han » sach danh, sach nang, sach dao
danh vi » hanh vi, dinh vi, danh di
truc va » thuc va, trung va
van cam » van nam, van lam, van cau
tang ma » mang may, tang van
su tien » su kien, su hien, tu tieng
ma hoi » mai hoi, xa hoi, ma hoa
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 han) or (sach tham)) tang ma hoi. hieu van cam ((truc va) OR (thuc vat)) danh vi su tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach han) OR (sach tham)) tang ma hoi. hieu van cam ((truc va) OR (thuc vat)) danh vi su tien*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach han) or (sach tham)) tang ma hoi. hieu van cam ((truc va) OR (thuc vat)) danh vi su tien*".