16253
In the search for the chemical measure of molecular aromaticity , namely the energetic gain of a cyclic delocalized structure for just being cyclic , the numerous definitions of generic aromatic stabilisation energies proposed hitherto stand as approximates of the conceptual limit devised within the framework of spectral graph theory , i . e . the topological resonance energy ( TRE ) .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
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