Takako Hashimoto Takeaki Uno Yuka Takedomi David Lawrence Shepard Masashi Toyoda Naoki Yoshinaga 0001 Masaru Kitsuregawa Ryota Kobayashi Two-stage Clustering Method for Discovering People's Perceptions: A Case Study of the COVID-19 Vaccine from Twitter. 614-621 2021 IEEE BigData https://doi.org/10.1109/BigData52589.2021.9671982 conf/bigdataconf/2021 db/conf/bigdataconf/bigdataconf2021.html#HashimotoUTST0K21