Extrinsic shape of circles and standard imbeddings of projective spaces. Toshiaki Adachi, S. Maeda, K. Ogiue (1997) Manuscripta mathematica
Extrinsic symmetric spaces and orbits of s-representations. E. Heintze, J.-H. Eschenburg (1995) Manuscripta mathematica
Extrinsic symmetric submanifolds contained in quaternionic symmetric spaces Miriam Pacheco, Cristián Sánchez (1998) Rendiconti del Seminario Matematico della Università di Padova