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Ecological systems theory , originally formulated by Urie Bronfenbrenner , specifies four types of nested environmental systems , with bi-directional influences within and between the systems .
 Urie Bronfenbrenner
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Urie Bronfenbrenner