Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
cau tren » cu tren, dau tren, ca tren
doc sach » toc sach, nuoc sach, dac sac
hieu va » lieu va, hieu qua
cuu tre » cua tre, cau treo
danh di » danh du, xanh di, danh dien
va danh » va dinh, va dan, va hanh
cam luc » cam xuc, cau luc
luc va » duc va, tuc va, loc va
nang o » nang co, nang ho, nang ro
v nang » va nang, vu nang, van nang
va cam » va cham, va cac, va cao
o hoi » co hoi, o hoc, o hai

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((hoc sach) or (doc sach)) v nang o hoi. hieu va cam luc va danh di ((cuu tre) OR (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((hoc sach) OR (doc sach)) v nang o hoi. hieu va cam luc va danh di ((cuu tre) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((hoc sach) or (doc sach)) v nang o hoi. hieu va cam luc va danh di ((cuu tre) OR (cau tren))".
• Adding a wildcard symbol may retrieve word variants: ((hoc sach) or (doc sach)) v nang o hoi. hieu va cam luc va danh di ((cuu tre) OR (cau tren))*.