@ARTICLE{Kato94logsmooth, author = {Fumiharu Kato}, title = {Log Smooth Deformation Theory}, journal = {Tohoku Math. J}, year = {1994}, volume = {48}, pages = {317--354}}
this article, we formulate and develop the theory of log smooth deformations. Here, log smoothness (more precisely, logarithmic smoothness) is a concept in log geometry