The phrase "a string of firms" is correct and usable in written English.
It can be used to describe a series or sequence of companies or businesses that are related in some way, such as being in the same industry or part of a supply chain.
Example: "The report highlighted a string of firms that have been collaborating on sustainable practices in the manufacturing sector."
Alternatives: "a series of companies" or "a chain of businesses".
It is the latest among a string of firms to warn about the effect of the national living wage.
In recent months, a string of firms, from fish factories in Grimsby to coffee shops in central London, have withdrawn overtime, Sunday pay, bonuses, free food and paid breaks in order to keep the wage bill down.
All told, Fiat spent euro6 billion in 1999 buying a string of firms to strengthen its non-car businesses.But Mr Fresco is adamant that car making will stay at the heart of Fiat's long-term strategy, despite the fact that the division has been a drag on profits.
Steve Case and JD Vance's Rise of the Rest seed fund is the latest in a string of firms betting on the Midwest (see also: Flyover Capital, M25 Group).
These days she can rattle off a string of firms with at least one female founder, including Nasty Gal, Who What Wear, Maker Studios, NuOrder and Shop Hers.
Followed by a string of firm denials at odds with mounting contradictory evidence, there was outrage, David Letterman jokes, and a less-than-graceful bowing out.
EVER since the implosion of Arthur Andersen, the giant accounting firm which acted as the auditor to Enron and a string of other firms which cooked their books, the auditing industry has been in turmoil.
The spending report also revealed a string of controversial firms are retained by the central NHS board.
Gruntal is the latest in a string of securities firms to cut jobs amid a slowdown in the investment banking business.
Matthew Freud has bought a £4m stake in the company that owns a string of PR firms including Citigate, Grayling and Red.
Twitter has become the latest in a string of Silicon Valley firms to face a gender discrimination lawsuit, forcing the male-dominated technology industry to grapple with widespread accusations of sexism.
