You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Genocide

Context:
In paragraph 13 the judges raise the issue of the perpetrators' access to the victims: "The historical examples of genocide also suggest that the area of the perpetrators’ activity and control, as well as the possible extent of their reach, should be considered. ... The intent to destroy formed by a perpetrator of genocide will always be limited by the opportunity presented to him. While this factor alone will not indicate whether the targeted group is substantial, it can—in combination with other factors—inform the analysis."

Question:
What is the basis for suggesting that several factors regarding the activity of the perpetrators be considered? 

historical examples of genocide