{
 "rule": "Euclidean: s < 0, t < 0 and u = -s - t < 4 m^2 (the domain of the closed dilogarithmic kernel and of the evaluator; a point outside it is refused by name). The four points provided here also keep u <= 2, so the kernel-analyticity margin 1 - u/4 is at least 1/2 (the smallest here 9/16; reference 2/3); sit at distances >= 9/4 from the u = 4 m^2 threshold (the two-fermion cut of the box's u-channel) and >= 17/4 from s = 4 m^2, the nearest letters; have rational heights comparable to the reference (denominators <= 4, |s|, |t| in [1/4, 3/2]); and their (|s|, |t|, |u|) multisets differ from the reference's {1/3, 1, 4/3} and from each other (a function comparison, not a crossing image). P1 and P4 lie on the line t = 2s (u = 3/2 and 3/4; -u/s = 3): there an odd-order Gauss-Legendre rule in the closed one-loop box would place a node exactly on a removable common zero of two of its factors; the box uses an even-order rule, which has no node there. Only these four points come with a reconstructed w'-DE and an independent AMFlow grid; any other (s, t) needs both and is refused by name.",
 "reference": {
  "s": "-1",
  "t": "-1/3",
  "msq": "1",
  "u": "4/3"
 },
 "points": [
  {
   "tag": "P1",
   "s": "-1/2",
   "t": "-1",
   "msq": "1",
   "u": "3/2",
   "one_minus_u_over_4": "5/8",
   "dist_u_threshold": "5/2",
   "dist_s_threshold": "9/2"
  },
  {
   "tag": "P2",
   "s": "-3/2",
   "t": "-1/4",
   "msq": "1",
   "u": "7/4",
   "one_minus_u_over_4": "9/16",
   "dist_u_threshold": "9/4",
   "dist_s_threshold": "11/2"
  },
  {
   "tag": "P3",
   "s": "-3/4",
   "t": "-1/2",
   "msq": "1",
   "u": "5/4",
   "one_minus_u_over_4": "11/16",
   "dist_u_threshold": "11/4",
   "dist_s_threshold": "19/4"
  },
  {
   "tag": "P4",
   "s": "-1/4",
   "t": "-1/2",
   "msq": "1",
   "u": "3/4",
   "one_minus_u_over_4": "13/16",
   "dist_u_threshold": "13/4",
   "dist_s_threshold": "17/4"
  }
 ]
}