Umezawa H., Matsumoto H., Tachiki M. Thermofield dynamics and condensed states. In Russian (ask us if in doubt)/Umedzava Kh., Matsumoto Kh., Tatiki M. Termopolevaya dinamika i kondensirovannye sostoyaniya. Translation from English. M. Mir 1985. 504 p. SKUalb3bf5409689e0a934.