"it is only required" is correct and can be used in written English.
It is often used to indicate that something is necessary or compulsory. Example: In order to enter the building, it is only required that visitors wear a mask.
Romney's Tyler Charitable Foundation has assets of roughly $10 million, of which it is only required to spend 5percentt per year to maintain its tax-preferred status.
It is only required that it be accepted (cf. Stalnaker 2002: 716).
It is only required that (p(0)neq0,1), which leads to G^{2}neq2H,3H.
In this approach it is only required that several backward Euler linear problems be solved, in serial or parallel.
However, in view of x which is K-sparse, it is only required to obtain K non-zero coefficients and their position.
Remark 2.3 In Lemma 2.2, it is only required that f is continuously differentiable near z and x j ( 0 ≤ j ≤ m − 1 ).
The Iranian government said it was only required to declare its existence to the IAEA six months before it intended to put radioactive material in it.
Paid sick leave would be affordable – only 23¢ an hour for private-sector workers and 81¢ an hour for state and government employees, according to the Bureau of Labor Statistics – but it's only required by law right now for 5.7 million people in the US, and the trend in the past few years has been towards fewer worker benefits, not more.
When setting, it's only required to set ingress direction threshold, and the egress direction flow rate don't need to be controlled, because the storm must be derived from the ingress direction.
In addition, it's only required to set flow rate threshold of edge ports (i.e. the switch ports directly connecting to IED equipment), and don't need to set link up port.
In some companies, it comes off that way because it's only required after an incident. .
