@inproceedings{Ansoldi:2008nH, author = "Ansoldi, Stefano", title = "{Vacuum and semiclassical gravity: a difficulty and its bewildering significance}", doi = "10.22323/1.043.0004", booktitle = "Proceedings of From Quantum to Emergent Gravity: Theory and Phenomenology {\textemdash} PoS(QG-Ph)", year = 2008, volume = "043", pages = "004" }