Various automated evaluation approaches are proposed to facilitate the development and evaluation of NLG models. We summarize these evaluation approaches below. Text Overlap Metrics, including BLEU BIBREF5, METEOR BIBREF6 and ROUGE BIBREF7, are the most popular metrics employed in the evaluation of NLG models. Perplexity is commonly used to evaluate the quality of a language model. Parameterized Metrics learn a parameterized model to evaluate generated text. 
 Question: What previous automated evalution approaches authors mention?
Text Overlap Metrics, including BLEU Perplexity Parameterized Metrics