I would say in this context

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Note added at 5 mins (2012-11-15 17:42:37 GMT)
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Forums or Fora?
Fora is sometimes cited as the correct plural for forum. Although it is indeed correct, there is some debate over whether it is the only correct pluralisation. Most online dictionaries provide both fora and forums as acceptable terms.

You will notice that we use the plural forums here at MediaCollege.com. This is for two reasons:

1.It appears to be acceptable English.
2.It is the pragmatic solution.
Whilst we are against most forms of language dumbing-down, we are also against unnecessary complication. Everyone knows and understands the word forums. Most people don't know what fora means. There is almost no chance of changing that situation significantly, no matter how hard the purists might want to. Like the failed Esperanto language, we believe reality wins over idealism. It's sad but inescapably true.

We don't believe it makes sense to promote fora as the "correct" pluralisation because it creates confusion, offers no real benefit, and can't work anyway so it's pointless trying.


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Note added at 6 mins (2012-11-15 17:43:43 GMT)
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I think something general and generic would be fine here

The use of the word 'tratados' suggests a more formal arrangement involving membership regulated by binding agreements and indeed the examples given: OIV, UE, Mercosur and OMC fit this description.

Spanish term (edited): otros tratados regionales o internacionales

I see what you mean. I reckon adding "parties to" would sort it ;-)