[WP][DOC] (issue7_refract): set section titles in comments

src/ts/refract/sub/refract_settracevp.f

@@ -135,6 +135,12 @@ c
       logical result
       real vppm, ttmin, ttmax, theoffset
       real realtime, plotoffset
+c 
+c ======================================================================
+c
+c 1. Operate on vertical coordinates, offset domain and world
+c    coordinates in counts.
+c ----------------------------------------------------------- 
 c
 c factor "world coordinates -> normalized device coordinates"
       vppm=(tov_vptop-tov_vpbot)/(tov_rmax-tov_rmin)
@@ -188,6 +194,13 @@ c check actual world coordinate range versus seismogram range
 c 
       if (result) then
 c
+c 
+c ======================================================================
+c
+c 2. Operate on horizontak coordinates, time domain and world
+c    coordinates in seconds.
+c ----------------------------------------------------------- 
+c
 c now check TIME SCALE
         ttmin=toffset(i)
         ttmax=toffset(i)+(nsamples(i)-1)*dt(i)