Question: Björn Ulvaeus was a part of a Swedish pop group, formed in Stockholm in 1972, as well as co-producer on the film "Mamma Mia!" with who?

full_context: Document 1: List of Europop artists: Europop refers to a style of pop music that first developed in today's form in Europe, throughout the late 1970s. Europop topped the charts throughout the 1980s and 1990s. Some Europop stars came from France, Germany, Italy, Ireland, Netherlands and the United Kingdom, but most were Swedish in origin. In the 1970s, such groups were primarily popular in continental countries, with the exception of the biggest Europop outfit ever, Swedish 4-piece ABBA, who achieved great success in the UK, where they scored a 19 top 10 singles and 9 chart-topping albums, and in North America and Australia. In the late 1980s and early 1990s, Roxette and Ace of Base led Europop in American and British mainstream audiences. In the 1990s, pop groups like the Spice Girls, Aqua, Backstreet Boys and singer DJ BoBo were strongly influenced by Europop. In the 2000s, one of the most popular representators of Europop music is Swedish pop group Alcazar. One of the main differences between American and European pop is that Europop is generally more dance and trance oriented. In central Europe, Italo disco (a.k.a. ’80s Eurodisco) and Euro house (a.k.a. ’90s Eurodance) (later) are the predominant attempts by young musicians to have a hit record in and beyond the borders of their own country.
Document 2: Benny Andersson: Göran Bror Benny Andersson (] ; born 16 December 1946) is a Swedish musician, composer, member of the Swedish music group ABBA (1972–1982), and co-composer of the musicals "Chess", "Kristina från Duvemåla", and "Mamma Mia!". For the 2008 film version of "Mamma Mia!", he worked also as an executive producer. Since 2001, he is active with his own band Benny Anderssons orkester.
Document 3: Björn Ulvaeus: Björn Kristian Ulvaeus (] ) (born 25 April 1945; credited as Björn Ulvæus) is a Swedish songwriter, producer, a former member of the Swedish musical group ABBA (1972–1982), and co-composer of the musicals "Chess", "Kristina från Duvemåla", and "Mamma Mia!". He co-produced the film "Mamma Mia!" with fellow ABBA member and close friend Benny Andersson.
Document 4: Börge Hellström: Börge Lennart Hellström (25 September 1957 – 17 February 2017) was a Swedish writer. A reformed criminal, he was perhaps best known as a founding member of the organisation "Kriminellas revansch i samhället" (KRIS). The organisation aims to combat crime and provide support to former criminals. He was also one half of the writing duo Roslund & Hellström. With journalist Anders Roslund, he co-authored seven books between 2004 and 2016.
Document 5: Mamma Mia! Original Cast Recording: Mamma Mia! Original Cast Recording is the original cast album for the 1999 English stage musical "Mamma Mia!". The album was released in 1999 and it reached No.56 in the UK album chart, with 2 weeks on the chart. Mamma Mia! reinvigorated the popularity of ABBA (the film soundtrack was the best-selling album of the week and several songs made the top #75 in the UK singles chart). The re-interest in this 1999 Original London Cast album caused it to reach #12 in the UK Album Chart, having charted at #16 a week earlier. It features performances by the original London cast of the musical including Lisa Stokke, Siobhán McCarthy and Hilton McRae. The album was produced by the two male members of ABBA, Benny Andersson and Bjorn Ulvaeus
Document 6: Torben Ulrich: Torben Ulrich (born October 4, 1928) is a Danish writer, musician, filmmaker, painter, director, performer and former amateur then professional tennis player. He is the father of Metallica drummer Lars Ulrich.
Document 7: ABBA: ABBA (] ) were a Swedish pop group, formed in Stockholm in 1972 by members Agnetha Fältskog, Björn Ulvaeus, Benny Andersson, and Anni-Frid Lyngstad. They became one of the most commercially successful acts in the history of popular music, topping the charts worldwide from 1974 to 1982. ABBA won the Eurovision Song Contest 1974 at The Dome in Brighton, UK, giving Sweden its first triumph in the contest, and are the most successful group to have ever taken part in the competition.
Document 8: Agnetha Fältskog: Agnetha Fältskog (] , born 5 April 1950) is a Swedish musician, singer, songwriter, actress, and author. She achieved success in Sweden after the release of her debut album "Agnetha Fältskog" in 1968, and reached international stardom as a member of the pop group ABBA, which has sold over 380 million albums and singles worldwide, making them one of the best-selling music artists in history.
Document 9: Super Trouper (song): "Super Trouper" is a single by Swedish pop group ABBA, and the title track from their 1980 studio album of the same name, written by Benny Andersson and Björn Ulvaeus. The song – with lead vocals by Anni-Frid Lyngstad – had the working title "Blinka Lilla Stjärna", and was the last track to be written and recorded for the album (ultimately replacing the track "Put On Your White Sombrero"). "Super Trouper" is included on the compilation album "", and also features in the musical "Mamma Mia!".
Document 10: Anni-Frid Lyngstad: Anni-Frid Synni, Princess Reuss of Plauen (German: "Anni-Frid Synni, Prinzessin Reuß von Plauen" ; born Anni-Frid Synni Lyngstad, 15 November 1945), commonly known as Frida Lyngstad, or just by the mononym, Frida, is a Norwegian-born Swedish singer, songwriter, and environmentalist. Known for her warm personality, striking auburn hair and rich mezzo-soprano voice, she is best known as one of the lead singers of the Swedish pop band, ABBA.
Document 11: Mamma Mia! The Movie Soundtrack: Mamma Mia! The Movie Soundtrack is the soundtrack album for the 2008 Universal Pictures musical film "Mamma Mia!", based on the stage musical of the same name. It features performances by the film's cast including Meryl Streep, Amanda Seyfried, Pierce Brosnan, Dominic Cooper, Stellan Skarsgård, Colin Firth, Julie Walters, Christine Baranski, Ashley Lilley, and Rachel McDowall. The recording was produced by Benny Andersson who along with Björn Ulvaeus had produced the original ABBA recordings. Also many of the musicians from the original ABBA recordings participated in making the soundtrack album. In keeping with the setting, the musical arrangements featured the use of traditional Greek instruments, most noticeably the bouzouki.
Document 12: Fernando (song): "Fernando" is a song by the Swedish pop group ABBA. It was the group's first non-album single and was released in March 1976 through Polar Music. The track was featured on the 1976 compilation album "Greatest Hits" in most countries, but was included on the group's fourth studio album "Arrival" in Australia and New Zealand. "Fernando" is also featured on the multi-million selling "" compilation. The song was to become one of ABBA's best-selling singles of all time, with six million copies sold in 1976 alone. It is one of fewer than forty all-time singles to have sold 10 million (or more) physical copies worldwide, making it one of the best selling singles of all time.
Document 13: Linda Ulvaeus: Linda Elin Ulvaeus (born 23 February 1973) is a Swedish singer-songwriter, screen and stage actress. She is the eldest child of Agnetha Fältskog and Björn Ulvaeus, former members of the Swedish pop group ABBA.
Document 14: Mamma Mia! (film): Mamma Mia! (promoted as Mamma Mia! The Movie) is a 2008 British-American-Swedish musical romantic comedy film adapted from the 1999 West End/2001 Broadway musical of the same name, based on the songs of successful pop group ABBA, with additional music composed by ABBA member Benny Andersson. The film was directed by Phyllida Lloyd and distributed by Universal Pictures in partnership with Tom Hanks and Rita Wilson's Playtone and Littlestar, and the title originates from ABBA's 1975 chart-topper "Mamma Mia". Meryl Streep heads the cast, playing the role of single mother Donna Sheridan. Pierce Brosnan (Sam Carmichael), Colin Firth (Harry Bright), and Stellan Skarsgård (Bill Anderson) play the three possible fathers to Donna's daughter, Sophie (Amanda Seyfried). "Mamma Mia!" received mixed reviews from critics and earned $609.8 million on a $52 million budget.
Document 15: Mamma Mia!: Mamma Mia! (promoted as Benny Andersson & Björn Ulvaeus' Mamma Mia! and Mamma Mia! The Smash Hit Musical) is a jukebox musical written by British playwright Catherine Johnson, based on the songs of ABBA, composed by Benny Andersson and Björn Ulvaeus, former members of the band. The title of the musical is taken from the group's 1975 chart-topper "Mamma Mia". Ulvaeus and Andersson, who composed the original music for ABBA, were involved in the development of the show from the beginning. Singer Anni-Frid Lyngstad has been involved financially in the production and she has also been present at many of the premieres around the world.
ground_truth: Benny Andersson