Perhaps you should try some spelling variations:
sach van » sach han, sach va, bach van
van nang » van quang, van ban, van dong
dieu cua » dieu tra
van hanh » van thanh, ban hanh, van anh
truc van » truc va, thuc van, truc ban
cam truc » cau truc, nam truc, lam truoc
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
ve cam » ve cham, ve cac, va cam
de cua » le cua, te cua
o hai » co hai, so hai, o lai
o hoi » co hoi, o hoc, 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: su sach van nang ((o hoi) or (o hai)). hieu ve cam truc van hanh ((de cua) OR (dieu cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach van nang ((o hoi) OR (o hai)). hieu ve cam truc van hanh ((de cua) OR (dieu cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach van nang ((o hoi) or (o hai)). hieu ve cam truc van hanh ((de cua) OR (dieu cua)) tre".
• Adding a wildcard symbol may retrieve word variants: su sach van nang ((o hoi) or (o hai)). hieu ve cam truc van hanh ((de cua) OR (dieu cua)) tre*.