Companion (Doctor Who) "Face the Raven", but in a subsequent episode ("Hell Bent") her time stream is frozen at the moment of death by the Time Lords so that they can interrogate her about the Hybrid; the Doctor takes advantage of this to save her life, but she remains technically neither alive nor dead, does not age or have a pulse. After her departure as a companion of the Twelfth Doctor, she teams with the immortal Ashildr and travels in a stolen TARDIS. Other companions died in alternate timelines or alternate lives. "Brigade Leader" Alistair Lethbridge-Stewart, "Section Leader" Liz Shaw, and "Platoon Leader"
The Princeton Companion to Mathematics Compared to the concise and factual coverage of mathematics in sources such as Wikipedia and MathWorld, the articles in the "Princeton Companion" are intended to be more reflective and discursive, and to convey the beauty and depth of modern mathematics. Quoting a passage from Bertrand Russell that "Pure Mathematics is the class of all propositions of the form "p" implies "q"", the editor of the "Companion" states that it "is about everything that Russell’s definition leaves out." The core sections of the "Companion" are aimed primarily at readers who are already familiar with mathematics at the undergraduate level. Much of