TY - JOUR AU - Hawkes, H.E. TI - On Quaternion Number-Systems JO - Mathematische Annalen PY - 1905 VL - 60 SP - 437 EP - 447 KW - hypercomplex number; associative finite dimensional algebra; classification; Scheffers' enumeration problem UR - http://eudml.org/doc/158200 ER -