Table 1. The description of data sources, search string and links.

Search engine	Search string	Links
Google Scholar	Diffusion model AND text generation	https://scholar.google.com/
IEEE Xplore	Text generation OR pre-trained language model	https://ieeexplore.ieee.org/
WoS	Diffusion model OR text generation	https://www.webofknowledge.com/
Arxiv	Diffusion model AND NLP	https://arxiv.org/