Kazuo Hosokawa Takehito Tsujimori Teruo Fujii Hayato Kaetsu Hajime Asama Yoji Kuroda Isao Endo Self-Organizing Collective Robots with Morphogenesis in a Vertical Plane. 2858-2863 1998 ICRA db/conf/icra/icra1998-4.html#HosokawaTFKAKE98