Companion (Doctor Who) companions too have been depicted in the revived era, such as Jo Grant (n/k/a Jo Jones)'s grandson Santiago Jones; and Sarah Jane Smith's parents, adopted son Luke Smith, adopted daughter Sky Smith, and alternate timeline fiancé Peter Dalton; and Alistair Lethbridge-Stewart's daughter Kate Stewart. Another change in the revived era is the depiction of many companions' pre-Doctor lives, particularly their childhoods; no companion was so depicted in the classic era, aside from John Benton being temporarily 'de-aged' by The Master. Companions Rose Tyler, Mickey Smith, Adelaide Brooke, Amy Pond, Rory Williams, River Song and Clara Oswald have all been portrayed
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