Just-infinite群

群論中一個無限群G稱為just-infinite，如果G的所有真商群都是有限群，也就是說所有非平凡正規子群都有有限指數。

• 無限循環群${\displaystyle C_{\infty }}$
• 無限二面體群${\displaystyle D_{\infty }}$
• 無限單群

• McCarthy, D., Infinite groups whose proper quotient groups are finite, I （页面存档备份，存于互联网档案馆）. Communications on Pure and Applied Mathematics. 1968, 21(6):545–562.
• McCarthy, D., Infinite groups whose proper quotient groups are finite, II （页面存档备份，存于互联网档案馆）. Communications on Pure and Applied Mathematics. 1970, 23(5):767–789.