The full answer is:

filing and service of an intervention requirement (or of a requirement to intervene, or of an impleading requirement), announcement (or notification) or countersuit (or counter-lawsuit or counterclaim)

First see:

https://www.google.com/search?q="filing and service"&rlz=1C1...

or Google “filing and service” with the inverted commas

Then:

According to the Σταμέλος-Χατζιμανώλη Λεξικό Νομικών Ορών:

Προσεπίκληση = bringing in a third party by litigant, requirement of a party to intervene, requirement of a party to interplead.

So, in this respect, see:

https://www.google.com/search?q="an intervention requirement...

or Google “an intervention requirement” with the inverted commas

or

https://www.google.com/search?q="a requirement to intervene"...

or Google “a requirement to intervene” with the inverted commas

and

https://www.google.com/search?q="a requirement to implead"&r...

or Google “a requirement to implead” with the inverted commas

Then, according to the Σταμέλος-Χατζιμανώλη Λεξικό Νομικών Ορών:

Ανακοίνωση = notice, notification, announcement, communication, etc.

And

Ανταγωγή = counterclaim, cross claim, cross-action, counter-action, cross-demand, counter-lawsuit (countersuit).


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Note added at 13 hrs (2021-08-04 06:50:28 GMT)
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Instead of "filing and service of", you could write, "taking and service of". See;

https://www.google.co.uk/search?q="the taking and service of...

or Google "the taking and service of" lawsuit, with the inverted commas.

Saying "the exercise and service of" does not appear to be at all common.