"had previously formed" is correct and can be used in written English.
It is used to refer to something that happened prior to or in the past. For example: The members had previously formed an alliance to protect their kingdom.
In 1992 the flow of lava shifted back to the Pu'u 'Ō'ō vent, where a cinder cone had previously formed.
Kibaki prepared for the December 2007 presidential and parliamentary elections by forming a new coalition, the Party of National Unity (PNU), which included some of the political parties that had previously formed his NARC coalition.
The other publishers, which along with Random House and Penguin had previously formed the Big Four, had their successes (Hachette publishes Ferguson and Flynn, while HarperCollins has Walliams and Mantel as standard-bearers) but made no inroads on the mega-conglomerate's dominance.
Holly Russell, a spokeswoman for GlaxoSmithKline -- which makes Wellbutrin and Zyban, two popular smoking cessation drugs, and a nicotine patch -- said she did not believe that the company had previously formed a partnership with a city, but added that it would consider such a request.
Other investors include IT services provider Neusoft Corporation (which Appconomy had previously formed a strategic alliance with) and previous backers Western Technology Investment and True Ventures.
Many traditional markets, which had previously formed along the streets, have been remodeled into arcade-type malls in Korea to reduce the inconveniences due to rain.
Atkinson, former founder and CEO of Mtivity (a marketing resource management software company), while Angus has previously formed a retail business in computing, two software development companies and a systems integration business, and was the technical author of the PageFusion PDF RIP server.
They are currently in the National Archives of the United Kingdom, having previously formed part of the Public Record Office.
Moreover, since no included genus has previously formed the basis of a family level name, we propose two new names at tribal rank for these lineages.
Genetic susceptibility for disease, combined with an environmental trigger, has previously formed the basis for explaining this risk for conditions with an autoimmune basis, such as inflammatory bowel disease (15, 21 ).
Of the 70 human proteins targeted for crystallization by in situ proteolysis, 54 had not previously formed crystals, and 16 had formed poor-diffracting crystals.
