MIT News: Exotic “second sound” phenomenon observed in pencil lead (March 14, 2019) [link]
Paper: “Observation of second sound in graphite at temperatures above 100 K,” S. Huberman*, R. A. Duncan*, K. Chen, B. Song, V. Chiloyan, Z. Ding, A. A. Maznev, G. Chen, and K. A. Nelson, Science DOI: 10.1126/science.aav3548 (2019) [url]