Open Procedure Pursuant To Art. 71 Of Legislative Decree 36/2023 And S.M.I., Preparatory To The Stipulation Of N. 9 Framework Agreements With A Single Economic Operator Ex. Art. 59, Paragraph 3, Of Legislative Decree 36/2023 For The Duration Of 36 Months With Effect From The Date Of Stipulation In Order To Guarantee The Management, Maintenance And Repair Service Of Thermal, Electric And Air Conditioning Systems