Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
qua pham » quan pham, quy pham, qua cham
tan tuan » tran tuan, than tuan, van tuan
tuan dai » toan dai, tuan tai, quang dai
su sach » so sach, vu sach
cua te » cua tu
o hoi » co hoi, o hoc, o hoa
o hai » co hai, so hai, o lai

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) or (hoc sach)) ky nang ((o hoi) OR (o hai)). hieu qua pham duc tan tuan dai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (hoc sach)) ky nang ((o hoi) OR (o hai)). hieu qua pham duc tan tuan dai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (hoc sach)) ky nang ((o hoi) OR (o hai)). hieu qua pham duc tan tuan dai cua te".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (hoc sach)) ky nang ((o hoi) OR (o hai)). hieu qua pham duc tan tuan dai cua te*.