\bex∑|\al|≤m\senD\al(fg)−(D\alf)gL2≤C\sex\senfL∞\sengHm+\senfHm−1\sen\ngL∞.\eex see [D. Chae, P. Degond, J.G. Liu, Well-posedness for Hall-magnetohydrodynamics, Ann. I. H. Poincar\'e-AN, 31 (2014),555--565].
\bex∑|\al|≤m\senD\al(fg)−(D\alf)gL2≤C\sex\senfL∞\sengHm+\senfHm−1\sen\ngL∞.\eex see [D. Chae, P. Degond, J.G. Liu, Well-posedness for Hall-magnetohydrodynamics, Ann. I. H. Poincar\'e-AN, 31 (2014),555--565].