diff --git a/swad_changelog.h b/swad_changelog.h
index 3477c077..e704fb2d 100644
--- a/swad_changelog.h
+++ b/swad_changelog.h
@@ -364,10 +364,11 @@ En OpenSWAD:
 ps2pdf source.ps destination.pdf
 */
 
-#define Log_PLATFORM_VERSION	"SWAD 18.28 (2019-01-07)"
+#define Log_PLATFORM_VERSION	"SWAD 18.28.1 (2019-01-07)"
 #define CSS_FILE		"swad18.22.css"
 #define JS_FILE			"swad17.17.1.js"
 /*
+	Version 18.28.1:  Jan 07, 2019 	Fixed bug in timetable related to groups. (239213 lines)
 	Version 18.28:    Jan 07, 2019 	Changes in edition of timetable related to classrooms. (239208 lines)
 					9 changes necessary in database:
 ALTER TABLE timetable_crs CHANGE COLUMN GroupName GroupName VARCHAR(2047) NOT NULL DEFAULT '';
diff --git a/swad_group.c b/swad_group.c
index 2e0b143b..b3e8d138 100644
--- a/swad_group.c
+++ b/swad_group.c
@@ -3021,10 +3021,10 @@ void Grp_GetListGrpTypesAndGrpsInThisCrs (Grp_WhichGroupTypes_t WhichGroupTypes)
                Grp->Classroom.ClaCod = Str_ConvertStrCodToLongCod (row[2]);
 
                /* Get classroom short name (row[3]) */
-               if (row[3])
+               if (row[3])	// May be NULL because of LEFT JOIN
 		  Str_Copy (Grp->Classroom.ShrtName,row[3],
 			    Cla_MAX_BYTES_SHRT_NAME);
-               else
+               else		// NULL
         	  Grp->Classroom.ShrtName[0] = '\0';
 
                /* Get number of current users in group */
@@ -3234,16 +3234,16 @@ void Grp_GetDataOfGroupByCod (struct GroupData *GrpDat)
      {
       /***** Get data of a group from database *****/
       NumRows = DB_QuerySELECT (&mysql_res,"can not get data of a group",
-				"SELECT crs_grp.GrpTypCod,"
-				       "crs_grp_types.CrsCod,"
-				       "crs_grp_types.GrpTypName,"
-				       "crs_grp_types.Multiple,"
-				       "crs_grp.GrpName,"
-				       "crs_grp.ClaCod,"
-				       "classrooms.ShortName,"
-				       "crs_grp.MaxStudents,"
-				       "crs_grp.Open,"
-				       "crs_grp.FileZones"
+				"SELECT crs_grp.GrpTypCod,"		// row[0]
+				       "crs_grp_types.CrsCod,"		// row[1]
+				       "crs_grp_types.GrpTypName,"	// row[2]
+				       "crs_grp_types.Multiple,"	// row[3]
+				       "crs_grp.GrpName,"		// row[4]
+				       "crs_grp.ClaCod,"		// row[5]
+				       "classrooms.ShortName,"		// row[6]
+				       "crs_grp.MaxStudents,"		// row[7]
+				       "crs_grp.Open,"			// row[8]
+				       "crs_grp.FileZones"		// row[9]
 				" FROM (crs_grp,crs_grp_types)"
 				" LEFT JOIN classrooms"
 				" ON crs_grp.ClaCod=classrooms.ClaCod"
@@ -3279,8 +3279,11 @@ void Grp_GetDataOfGroupByCod (struct GroupData *GrpDat)
 	 GrpDat->Classroom.ClaCod = Str_ConvertStrCodToLongCod (row[5]);
 
 	 /* Get the name of the classroom (row[6]) */
-	 Str_Copy (GrpDat->Classroom.ShrtName,row[6],
-	           Grp_MAX_BYTES_GROUP_NAME);
+	 if (row[6])	// May be NULL because of LEFT JOIN
+	    Str_Copy (GrpDat->Classroom.ShrtName,row[6],
+		      Cla_MAX_BYTES_SHRT_NAME);
+	 else		// NULL
+	    GrpDat->Classroom.ShrtName[0] = '\0';
 
 	 /* Get maximum number of students (row[7]) */
 	 GrpDat->MaxStudents = Grp_ConvertToNumMaxStdsGrp (row[7]);
diff --git a/swad_timetable.c b/swad_timetable.c
index 0e44adbd..592617e3 100644
--- a/swad_timetable.c
+++ b/swad_timetable.c
@@ -1520,10 +1520,10 @@ static void TT_TimeTableDrawCell (unsigned Weekday,unsigned Interval,unsigned Co
 
 	    /***** Group *****/
 	    if (Gbl.TimeTable.View == TT_CRS_VIEW &&
-	        GrpCod > 0)
+		GrpCod > 0)
 	      {
 	       fprintf (Gbl.F.Out,"<br />%s"
-		                  "<br />%s",
+				  "<br />%s",
 			GrpDat.GrpTypName,GrpDat.GrpName);
 	       if (GrpDat.Classroom.ClaCod > 0)
 		  fprintf (Gbl.F.Out,"<br />(%s)",
@@ -1531,8 +1531,9 @@ static void TT_TimeTableDrawCell (unsigned Weekday,unsigned Interval,unsigned Co
 	      }
 
 	    /***** Info *****/
-	    if (Info[0])
-	       fprintf (Gbl.F.Out,"<br />%s",Info);
+	    if (Info)
+	       if (Info[0])
+	          fprintf (Gbl.F.Out,"<br />%s",Info);
 
 	    /***** End cell *****/
             fprintf (Gbl.F.Out,"</div>");
@@ -1670,7 +1671,9 @@ static void TT_TimeTableDrawCell (unsigned Weekday,unsigned Interval,unsigned Co
 			CellStr,
 		        Txt_Info,
 			CellStr,
-			TT_MAX_CHARS_INFO,Info,
+			TT_MAX_CHARS_INFO,
+			Info ? Info :
+			       "",
 			Gbl.Form.Id);
 	      }
 	    else // TimeTableView == TT_TUT_EDIT
diff --git a/swad_timetable.h b/swad_timetable.h
index 13c1349a..039a1691 100644
--- a/swad_timetable.h
+++ b/swad_timetable.h
@@ -36,9 +36,6 @@
 #define TT_MAX_CHARS_INFO	(128 - 1)	// 127
 #define TT_MAX_BYTES_INFO	((TT_MAX_CHARS_INFO + 1) * Str_MAX_BYTES_PER_CHAR - 1)	// 2047
 
-// #define TT_MAX_CHARS_PLACE	(32 - 1)	// 31
-// #define TT_MAX_BYTES_PLACE	((TT_MAX_CHARS_INFO + 1) * Str_MAX_BYTES_PER_CHAR - 1)	// 511
-
 typedef enum
   {
    TT_CRS_VIEW,