Anders, O., Cockrell, D.C., Dale, H., Fischer, E.R., Virtaneva, K., Sturdevant, D.E., Porcella, S.F. and Heinzen, R.A. (2009) Host Cell-Free Growth of the Q Fever Bacterium Coxiella burnetii. Proceedings of the National Academy of Sciences of the United States of America, 106, 4430-4434.