https://dds.las.ac.cn/service/document?appId=a1vacbnPuv9qJRzJvdNXfsesj9JbIa6e&appKey=sPBA4vANLzjnW1k5eufEcc4k7dxfNraW&ts=1763013962752&signature=ce77da38483d8555526eb56175584bd0&articleTitle=Theory+of+Oscillators&articleAuthor=Andronov%2C+A.+A.&publicationTitle=Theory+of+Oscillators&language=&publicationType=1&publishYear=&isn=9781483167244&publisher=