p.boxed.
  Kings are subject to check and checkmate by own as well as opponent's pieces.

p.
  Kings are attacked by all pieces, and can capture any piece.
  For example, on the following diagram the king can escape check by
  capturing a rook.

figure.diagram-container
  .diagram
    | fen:8/8/8/8/8/4q4/8/3RKR2:
  figcaption Not a checkmate: Kxf1 or Kxd1.

p.
  Here however, each capture of the queen would lead to a self-check: although
  the queen appears vulnerable this is a checkmate.

figure.diagram-container
  .diagram
    | fen:1r1nkbr1/1p2Qnp1/p2p1p1p/2p4P/P1P1P3/1P6/R2P1KP1/2B2BNR:
  figcaption Checkmate.

h3 Source

p
  a(href="https://www.jsbeasley.co.uk/encyc.htm")
    | The Classified Encyclopedia of Chess Variants.
  |  by David B. Pritchard (2007).

p Inventors: Gabriel Authier and Roméo Bédoni (1958)