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Priority to JP1983021551UpriorityCriticalpatent/JPS59129245U/ja
Publication of JPS59129245UpublicationCriticalpatent/JPS59129245U/ja
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Publication of JPH0110033Y2publicationCriticalpatent/JPH0110033Y2/ja
Key hole insertion for manhole and manhole cover locking apparatus equipped with the key hole insertion and manhole cover locking system and unlocking method and manhole cover opening and closing control system