Question: When was the band for which Bob Welch was a guitarist formed ?

full_context: Document 1: Fleetwood Mac: Fleetwood Mac are a British-American rock band, formed in London in 1967. The band have sold more than 100 million records worldwide, making them one of the world's best-selling bands of all time. In 1998, selected members of Fleetwood Mac were inducted into the Rock and Roll Hall of Fame, and received the Brit Award for Outstanding Contribution to Music.
Document 2: Rumours (album): Rumours is the eleventh studio album by British-American rock band Fleetwood Mac. Largely recorded in California during 1976, it was produced by the band with Ken Caillat and Richard Dashut and was released on 4 February 1977 by Warner Bros. Records. The record reached the top of both the United States "Billboard" chart and the United Kingdom Albums Chart. The songs "Go Your Own Way", "Dreams", "Don't Stop", and "You Make Loving Fun" were released as singles. "Rumours" is Fleetwood Mac's most successful release; along with winning the Grammy Award for Album of the Year in 1978, the album has sold over 40 million copies worldwide, making it one of the best-selling albums of all time. "Rumours" has received diamond certifications in several countries, including the US, Canada, and Australia.
Document 3: Bob Welch Looks at Bop: Bob Welch Looks At Bop is the seventh solo studio album by Bob Welch. After a 16 year self-imposed retirement, it was his first new recording since "Eye Contact" was released in 1983. Welch is the only musician credited on the album (except for one backing vocal by Beegie Adair), but he has stated in an interview that there were others involved by way of "modern technology". The cover states that this is his first studio album since 1977's "French Kiss," which is not true since Welch released five follow-up albums after French Kiss. Welch would not record another album until his 2003 recording "His Fleetwood Mac Years & Beyond".
Document 4: Lindsey Buckingham: Lindsey Adams Buckingham (born October 3, 1949) is an American musician, singer, songwriter, and producer, best known as lead guitarist and one of the vocalists of the musical group Fleetwood Mac from 1975 to 1987, and then 1997 to the present day. Aside from his tenure with Fleetwood Mac, Buckingham has also released six solo albums and three live albums. As a member of Fleetwood Mac, he was inducted into the Rock and Roll Hall of Fame in 1998. In 2011, Buckingham was ranked 100th in Rolling Stone Magazine's 2011 list of "The 100 Greatest Guitarists of All Time". Buckingham is known for his fingerpicking guitar style.
Document 5: His Fleetwood Mac Years and Beyond, Vol. 2: All songs written by Bob Welch except Black Magic Woman by Peter Green, Rhiannon by Stevie Nicks, Two Sides To Beautiful by Bob Welch & Bob Mylan & World Turning by Lindsey Buckingham & Christine McVie.
Document 6: Steve Miller Band: The Steve Miller Band is an American rock band formed in 1966 in San Francisco, California. The band is led by Steve Miller on guitar and lead vocals. It is best known today for a string of (mainly) mid-1970s hit singles that are staples of classic rock radio, as well as several earlier acid rock albums. Miller left his first band to move to San Francisco and form the Steve Miller Blues Band. Shortly after Harvey Kornspan negotiated the band’s landmark contract with Capitol Records in 1967, the band shortened its name to the Steve Miller Band. In February 1968, the band recorded its debut album, "Children of the Future". It went on to produce the albums "Sailor", "Brave New World", "Your Saving Grace", "Number 5", "Rock Love" and more. The band's "Greatest Hits 1974–78", released in 1978, sold over 13 million copies. The band continued to produce more albums and in 2014 toured with the rock band Journey. In 2016, Steve Miller was inducted as a solo artist in the Rock and Roll Hall of Fame.
Document 7: The Chain: "The Chain" is a song by the British-American rock band Fleetwood Mac, released on their best-selling album "Rumours". It is the only song from the album credited to all five members (Stevie Nicks, Lindsey Buckingham, Christine McVie, John McVie, and Mick Fleetwood).
Document 8: Head West: Head West is a music album released in 1970 by the American band Head West, who were based in Paris, France. The band are best known today for their vocalist / guitarist Bob Welch, who went on to join Fleetwood Mac in 1971. Since 1973, by which time Welch had become more well-known, the album was repackaged as more of a solo album, credited to Bob Welch with Head West. Singles were also released but with little success.
Document 9: Dreams (Fleetwood Mac song): "Dreams" is a song by British-American rock band Fleetwood Mac from their eleventh studio album "Rumours" (1977). In the United States, "Dreams" was released as the second single from "Rumours" on March 24, 1977, while in the United Kingdom it was released as the third single in June 1977. A performance of "Dreams" on stage was used as the promotional music video.
Document 10: His Fleetwood Mac Years &amp; Beyond: Bob Welch: His Fleetwood Mac Years & Beyond was an album of rerecordings of songs by former Fleetwood Mac guitarist turned solo artist Bob Welch. As the title suggests, most of the songs were rerecordings of songs he had written and recorded both with Fleetwood Mac and solo. The album also contained a recording of "Oh Well", a Mac hit from before Welch's time in the group, that he sang many times after Peter Green's departure; and a brand new track, "Like Rain". The album was re-released with a different track order in 2008 as Greatest Hits & More - Revisited.
Document 11: French Kiss (Bob Welch album): French Kiss is the solo debut by former Fleetwood Mac singer/guitarist Bob Welch. The songs, with the exception of "Sentimental Lady", were intended for a projected third album by Welch's previous band, Paris. However, the group fell apart in 1977 before recording could begin. So instead, Welch used these songs for his debut solo album.
Document 12: The Other One: The Other One is the third solo album by former Fleetwood Mac guitarist Bob Welch. The track "Future Games" was first released on the Fleetwood Mac album of the same name in 1971. Members of Welch's backing band also make songwriting contributions here though the majority of tracks are Welch's own.
Document 13: Tusk (album): Tusk is the twelfth album by British-American rock band Fleetwood Mac. Released as a double album in 1979, it is considered experimental, primarily due to Lindsey Buckingham's sparser songwriting arrangements and the influence of punk rock and new wave on his production techniques. Widely noted in the 1979 press for costing over $1 million to record (equivalent to $ in 2016 ), it was the most expensive rock album made up to that point. Compared to 1977's "Rumours" which sold 10 million copies by February 1978, "Tusk" sold four million copies. Because of this, the album was regarded as a commercial failure by the label.
Document 14: Three Hearts: Three Hearts is the second solo album by rock musician and former Fleetwood Mac guitarist Bob Welch.
Document 15: Lindsey Buckingham/Christine McVie: Lindsey Buckingham/Christine McVie (also referred to as simply Buckingham/McVie) is a studio album by Fleetwood Mac vocalists Lindsey Buckingham and Christine McVie, released on June 9, 2017. Four of the five members of Fleetwood Mac are featured in the album, with contributions from drummer Mick Fleetwood and bassist John McVie. Vocalist Stevie Nicks is the sole member absent in the album. The album sold over 22,000 units in the US in its first week and debuted within the top 20. It proved to be even more successful in the UK, where it debuted within the top 5.
ground_truth: 1967