Perhaps you should try some spelling variations:
sach hay » sach han, sach ha, sach nay
hay tang » ha tang, hao tang, tay tang
tang hoa » hang hoa, tang ha, tang ho
tu sach » thu sach, su sach, te sach
doi cua » dai cua, hoi cua
hoc ban » hoc bang, hoc bai, hoc can
hoa hoi » khoa hoi, hoa hoc, hoa doi
ky cau » ky chau, ke cau
di cua » dai cua, de cua, do cua

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 hay tang hoa hoi. hieu ky cau ((hoc ban) or (hoc dan)) hanh ((di cua) OR (doi cua)) te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach hay tang hoa hoi. hieu ky cau ((hoc ban) OR (hoc dan)) hanh ((di cua) OR (doi cua)) te*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach hay tang hoa hoi. hieu ky cau ((hoc ban) or (hoc dan)) hanh ((di cua) OR (doi cua)) te*".