Perhaps you should try some spelling variations:
truc tuan » truc quan, truc tuyen, trung tuan
sach van » sach va, bach van, cach van
sach han » sach tham, sach danh, sach nang
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
ve cau » ke cau, va cau, ve cac
anh le » manh le, oanh le, anh ve
le cua » ly cua
o hoc » co hoc, mo hoc, so hoc
o hoi » co hoi, o hai, o hoa

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 van) OR (sach han)) dong ((o hoi) or (o hoc)). hieu ve cau truc tuan anh le cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach van) OR (sach han)) dong ((o hoi) OR (o hoc)). hieu ve cau truc tuan anh le cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((sach van) OR (sach han)) dong ((o hoi) or (o hoc)). hieu ve cau truc tuan anh le cua tre".
• Adding a wildcard symbol may retrieve word variants: so ((sach van) OR (sach han)) dong ((o hoi) or (o hoc)). hieu ve cau truc tuan anh le cua tre*.