Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
cham hoc » cham soc, chat hoc, cham hoi
mai khoi » mai khoa, cac khoi, dai khoa
tai khoa » da khoa, noi khoa
hanh vai » hanh vi, hanh tai, hanh van
hanh va » hang va, hanh vi
tu sach » thu sach, su sach, te sach
ve cham » va cham, ve chat, vu cham
hieu ve » hieu va, hieu van
y sang » _ sang, duy sang

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 y sang ((mai khoi) or (tai khoa)). hieu ve cham hoc va ((hanh vai) or (hanh va)) cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y sang ((mai khoi) OR (tai khoa)). hieu ve cham hoc va ((hanh vai) OR (hanh va)) cau tren.
• Adding a wildcard symbol may retrieve word variants: tu sach y sang ((mai khoi) or (tai khoa)). hieu ve cham hoc va ((hanh vai) or (hanh va)) cau tren*.