same_order(x1;y1;x2;y2;L;T) == x1 << y1  L  (x2  L)  (y2  L)  x2 << y2  L 

latex

---

clarification:

same_order(x1;y1;x2;y2;L;T)
== strong_before(x1; y1; L; T)  (x2  L  T)  (y2  L  T)  strong_before(x2; y2; L; T) 

latex

Definitions	P  Q, (x  l), x << y  l
FDL editor aliases	same_order