Question: Who has won the Nobel Prize in the same category twice?

Context paragraphs:
Nobel Prize in Physiology or Medicine: The Nobel Prize in Physiology or Medicine (Swedish: "Nobelpriset i fysiologi eller medicin" ), administered by the Nobel Foundation, is awarded once a year for outstanding discoveries in the fields of life sciences and medicine.  It is one of five Nobel Prizes established in 1895 by Swedish chemist Alfred Nobel, the inventor of dynamite, in his will.  Nobel was personally interested in experimental physiology and wanted to establish a prize for progress through scientific discoveries in laboratories.  The Nobel Prize is presented to the recipient(s) at an annual ceremony on 10 December, the anniversary of Nobel's death, along with a diploma and a certificate for the monetary award.  The front side of the medal provides the same profile of Alfred Nobel as depicted on the medals for Physics, Chemistry, and Literature; its reverse side is unique to this medal.

List of Danish Nobel laureates: This is a list of Danish Nobel laureates.  Since the Nobel Prize was established per the will of Swedish inventor Alfred Nobel in 1895, 12 of the prize winners have been from Denmark.  The first Danish Nobel laureate was Niels Ryberg Finsen, who won a Nobel Prize for medicine in 1903 for his work in using light therapy to treat diseases.  The most recent Danish Nobel Prize winner was Jens Skou who won the prize in chemistry for his discovery over the enzyme, Na+/K+-ATPase in 1997.  To date, of the 13 Nobel Prizes won by Danish people, 5 have been for medicine, 3 have been for physics, 3 have been for literature, 1 has been for chemistry and one has been for peace.

John Bardeen: John Bardeen ( ; May 23, 1908 – January 30, 1991) was an American physicist and electrical engineer, the only person to have won the Nobel Prize in Physics twice: first in 1956 with William Shockley and Walter Brattain for the invention of the transistor; and again in 1972 with Leon N Cooper and John Robert Schrieffer for a fundamental theory of conventional superconductivity known as the BCS theory.

Nobel Prize in Literature: Since 1901, the Nobel Prize in Literature (Swedish: "Nobelpriset i litteratur" ) has been awarded annually to an author from any country who has, in the words of the will of Alfred Nobel, produced "in the field of literature the most outstanding work in an ideal direction" (original Swedish: "den som inom litteraturen har producerat det mest framstående verket i en idealisk riktning").  Though individual works are sometimes cited as being particularly noteworthy, here "work" refers to an author's work as a whole.  The Swedish Academy decides who, if anyone, will receive the prize in any given year.  The academy announces the name of the chosen laureate in early October.  It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895; the others are the Nobel Prize in Chemistry, Nobel Prize in Physics, Nobel Peace Prize, and Nobel Prize in Physiology or Medicine.

List of female Nobel laureates: The Nobel Prizes are awarded annually by the Royal Swedish Academy of Sciences, the Swedish Academy, the Karolinska Institute, and the Norwegian Nobel Committee to individuals who make outstanding contributions in the fields of Chemistry, Physics, Literature, Peace, Physiology or Medicine and Economics.  All but the economics prize were established by the 1895 will of Alfred Nobel, which dictates that the awards should be administered by the Nobel Foundation.  The Nobel prize in Economics, or The Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel, was established in 1968 by the Sveriges Riksbank, the central bank of Sweden, for outstanding contributions in the field of Economics.  Each prize is awarded by a separate committee; the Royal Swedish Academy of Sciences awards the Prizes in Physics, Chemistry, and Economics, the Swedish Academy awards the Prize in Literature, the Karolinska Institute awards the Prize in Physiology or Medicine, and the Norwegian Nobel Committee awards the Prize in Peace.  Each recipient receives a medal, a diploma and a cash prize that has varied throughout the years.

Frederick Sanger: Frederick Sanger ( ; 13 August 1918 – 19 November 2013) was a British biochemist who twice won the Nobel Prize in Chemistry, one of only two people to have done so in the same category (the other is John Bardeen in physics), the fourth person overall with , and the third person overall with two Nobel Prizes in the sciences.  In 1958, he was awarded a Nobel Prize in chemistry "for his work on the structure of proteins, especially that of insulin".  In 1980, Walter Gilbert and Sanger shared half of the chemistry prize "for their contributions concerning the determination of base sequences in nucleic acids".  The other half was awarded to Paul Berg "for his fundamental studies of the biochemistry of nucleic acids, with particular regard to recombinant DNA".

Nobel Prize in Physics: The Nobel Prize in Physics (Swedish: "Nobelpriset i fysik" ) is a yearly award given by the Royal Swedish Academy of Sciences for those who conferred the most outstanding contributions for mankind in the field of physics.  It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895 and awarded since 1901; the others being the Nobel Prize in Chemistry, Nobel Prize in Literature, Nobel Peace Prize, and Nobel Prize in Physiology or Medicine.

List of Nobel laureates in Physiology or Medicine: The Nobel Prize in Physiology or Medicine (Swedish: "Nobelpriset i fysiologi eller medicin" ) is awarded annually by the Swedish Karolinska Institute to scientists and doctors in the various fields of physiology or medicine.  It is one of the five Nobel Prizes established by the 1895 will of Alfred Nobel (who died in 1896), awarded for outstanding contributions in chemistry, physics, literature, peace, and physiology or medicine.  As dictated by Nobel's will, the award is administered by the Nobel Foundation and awarded by a committee that consists of five members and an executive secretary elected by the Karolinska Institute.  While commonly referred to as the Nobel Prize in Medicine, Nobel specifically stated that the prize be awarded for "physiology or medicine" in his will.  Because of this, the prize can be awarded in a broader range of fields.  The first Nobel Prize in Physiology or Medicine was awarded in 1901 to Emil Adolf von Behring, of Germany.  Each recipient receives a medal, a diploma and a monetary award that has varied throughout the years.  In 1901, von Behring received 150,782 SEK, which is equal to 7,731,004 SEK in December 2008.  In 2013, the prize was awarded to James E. Rothman, Randy W. Schekman and Thomas C. Südhof; they were recognised "after discovering how cells precisely transport material".  The award is presented in Stockholm at an annual ceremony on December 10, the anniversary of Nobel's death.

List of Nobel laureates by university affiliation: This list of Nobel laureates by university affiliation shows the university affiliations of winners of the Nobel Prize and the Nobel Memorial Prize in Economic Sciences since 1901 (total 881 individual laureates).  Although this list does not include organizations which were awarded the Nobel prize or any individuals in those organizations, a person who received the Nobel prize while working at a research organization formally affiliated with or operated by a university is counted as an affiliate of that university.  Universities are listed in descending order according to the number of affiliates, while only the top 50 universities are shown explicitly with their ranking.

Ada Yonath: Ada E. Yonath (Hebrew: עדה יונת‎ ‎ , ] ) (born 22 June 1939) is an Israeli crystallographer best known for her pioneering work on the structure of the ribosome.  She is the current director of the Helen and Milton A. Kimmelman Center for Biomolecular Structure and Assembly of the Weizmann Institute of Science.  In 2009, she received the Nobel Prize in Chemistry along with Venkatraman Ramakrishnan and Thomas A. Steitz for her studies on the structure and function of the ribosome, becoming the first Israeli woman to win the Nobel Prize out of ten Israeli Nobel laureates, the first woman from the Middle East to win a Nobel prize in the sciences, and the first woman in 45 years to win the Nobel Prize for Chemistry.  However, she said herself that there was nothing special about a woman winning the Prize.

Supporting paragraphs: Frederick Sanger John Bardeen
Answer: who twice won the Nobel Prize in Chemistry, one of only two people to have done so in the same category (the other is John Bardeen in physics)