"firstly required to" is correct and usable in written English.
You can use it to introduce an action that is required of someone or something, as in this example: "The workers were firstly required to fill out a safety checklist before beginning their shift."
The benefit to account holders is, as you may recall, twofold: firstly, they are required to pay only £9 to enter the Central zone compared with £10 for non-account holders; secondly, paying automatically means they aren't at risk of being fined for late payment.
Firstly, trustees are required to make sure that agent is suitable for the job he is employed to do.
Firstly, the time required to concentrate the community by filtration is longer than the half-life of mRNA, but this is true of most methods used to analyze the metatranscriptome of aquatic samples [6].
This may have occurred because, firstly, respondents were required to complete six conjoint surveys.
Firstly, research is required to understand how electronic health record data are coded historically under-resourced and lacking audit against quality standards and how this can be improved.
Firstly, our subjects were required to access simulated vessels in an ultrasound phantom, as opposed to the real vessels in a living human patient.
The study had to overcome two major challenges: firstly that participants were required to attend for four scans (three PET and one MRI), and secondly the recruitment of opioid-dependent individuals without co-morbid stimulant or benzodiazepine abuse.
In addition, specialist editorial tools and data maintenance procedures are required, to firstly add the value-added information to the original dataset and to subsequently maintain both dataset and meta-data in line with changes to our understanding of underlying reference resources such as genome/protein sequences or updates to the ontologies used to annotate the information.
Firstly, the bacteria are not required to grow in culture; this is critical as the fastidious nature of the majority of microorganisms associated with preterm delivery means that culture techniques may under-report the true prevalence.
