Question: Christopher Isherwood and Charles Reznikoff, have which mutual nationality?

Context paragraphs:
Prater Violet: Prater Violet (1945) is Christopher Isherwood's fictional first person account of film-making.  The Prater is a large park and amusement park in Vienna, a city important to characters in the novel for several reasons.  Though Isherwood broke onto the literary scene as a novelist, he eventually worked in Hollywood as a screenwriter.  In this novel, Isherwood comments on life, art, commercialization of art and Nazism.

Christopher and His Kind (film): Christopher and His Kind is a 2011 BBC television film.  It tells the story of Christopher Isherwood's life in Berlin in the early 1930s.  The film, adapted by Kevin Elyot from Isherwood's autobiography "Christopher and His Kind", was produced by Mammoth Screen and directed by Geoffrey Sax.  Isherwood is played by Matt Smith, whilst the cast also includes Toby Jones, Douglas Booth, Imogen Poots and Iddo Goldberg.

Sally Bowles: Sally Bowles is a fictional character created by Christopher Isherwood.  She originally appeared in Isherwood's 1937 novella "Sally Bowles" published by Hogarth Press.  The story was later republished in the novel "Goodbye to Berlin".

Christopher Isherwood: Christopher William Bradshaw Isherwood (26 August 1904 – 4 January 1986) was an English-American novelist.  His best-known works include "The Berlin Stories" (1935-39), two semi-autobiographical novellas inspired by Isherwood's time in Weimar Republic Germany.  These enhanced his postwar reputation when they were adapted first into the play "I Am a Camera" (1951), then the 1955 film of the same name, "I Am a Camera (film)"; much later (1966) into the bravura stage musical "Cabaret (musical)" which was acclaimed on Broadway, its unsparing stance being substantially sweetened for the film "Cabaret" (1972).  His novel "A Single Man" was published in 1964.

Mr Norris Changes Trains: Mr Norris Changes Trains (published in the United States as "The Last of Mr. Norris") is a 1935 novel by the British writer Christopher Isherwood.  It is frequently included with "Goodbye to Berlin", another Isherwood novel, in a single volume, "The Berlin Stories".  Inspiration for the novel was drawn from Isherwood's experiences as an expatriate living in Berlin during the early 1930s, and the character of Mr Norris is based on Gerald Hamilton.

Charles Reznikoff: Charles Reznikoff (August 31, 1894 – January 22, 1976) was an American poet best known for his long work, "Testimony: The United States (1885-1915), Recitative" (1934-1979).  The term Objectivist was coined for him.  The multi-volume "Testimony" was based on court records and explored the experiences of immigrants, black people and the urban and rural poor in the United States in the late nineteenth and early twentieth centuries.  He followed this with "Holocaust" (1975), based on court testimony about Nazi death camps during World War II.

The Memorial: The Memorial is a 1932 English novel by author Christopher Isherwood.  The novel tells the story of an English family's disintegration in the days following World War I.  Isherwood's second published novel, this is the first of his works for which he adapted his own life experiences into his fiction.

I Am a Camera (film): I Am a Camera is a British comedy-drama film released in 1955.  Based on "The Berlin Stories" by Christopher Isherwood and the play "I Am a Camera" by John Van Druten, the film is a fictionalized account of Isherwood's time living in Berlin between the World Wars.  Directed by Henry Cornelius from a script by John Collier, "I Am a Camera" stars Laurence Harvey as Isherwood and Julie Harris recreating her Tony Award winning performance as Sally Bowles.

The World in the Evening: The World in the Evening by Christopher Isherwood is a quasi-fictional account of love, loss, and regret.  As in many Isherwood novels, the main character is caught in a contest between his personal egoism and the needs of friends and lovers.  This novel has been praised for its narrator's definitions of high and low camp.

Vidyatmananda: Swami Vidyatmananda (29 July 1913 – 22 March 2000) was born John Yale.  He studied under Swami Prabhavananda at the Vedanta Society of Southern California and was ordained as a monk of the Ramakrishna Mission in 1964.  He traveled to India and recorded his impressions in the book, "A Yankee and the Swamis: A Westerner's View of the Ramakrishna Order".  He also edited the journal "Vedanta and the West" and compiled a selection of the teachings of Swami Vivekananda in "What Religion Is: In the Words of Swami Vivekananda" which contains an introduction by Christopher Isherwood.  He was an assistant to Swami Ritajananda at the Centre Védantique Ramakrishna in Gretz, France, where he served as the center's manager until his death on March 22, 2000 at the age of 86.  He edited the magazine "Vedanta and the West" and corresponded with many Western intellectuals including Aldous Huxley, Christopher Isherwood, Walter de la Mare, E. M. Forster, and Gerald Heard.  His autobiography "The Making of a Devotee" reveals his spiritual evolution.

Supporting paragraphs: Christopher Isherwood Charles Reznikoff
Answer: American