https://dds.las.ac.cn/service/document?appId=a1vacbnPuv9qJRzJvdNXfsesj9JbIa6e&appKey=sPBA4vANLzjnW1k5eufEcc4k7dxfNraW&ts=1763030135784&signature=11e177d2e8574b0d2c885f7cbfa694ed&articleTitle=Computable+Structures+and+the+Hyperarithmetical+Hierarchy&articleAuthor=C.J.+Ash%2C+J.+Knight&publicationTitle=Computable+Structures+and+the+Hyperarithmetical+Hierarchy&language=&publicationType=1&publishYear=&isn=9780444500724&publisher=