Format/typo check 2013/morgan1

I also included the dates for the two unnamed undated comets that the
author referred to so that one can see what is meant: Comet Halley and
Comet Hale-Bopp, labelled Ha and Hb in the program which is now noted in
the README.md file too.

2013/morgan1/README.md

@@ -18,6 +18,10 @@ echo "2013/10/03" | ./morgan1
 echo "1985/10/28" | ./morgan1
 
 echo "1996/12/31" | ./morgan1
+
+echo "1986/03/31" | ./morgan1 # Comet Halley (look for 'Ha')
+
+echo "1997/04/01" | ./morgan1 # Comet Hale-Bopp (look for 'Hb')
 ```
 
 Try pressing the arrow keys when your focus is in the window.
@@ -50,35 +54,49 @@ calendar](https://en.wikipedia.org/wiki/Julian_calendar) and
 [Gregorian calendar](https://en.wikipedia.org/wiki/Gregorian_calendar) (10 days
 missing between 1582/10/04 and 1582/10/15).
 
-The scale is logarithmic to be able to display the 8 planets without having
-Mercury, Venus, Earth and Mars squeezed around the Sun.
+The scale is logarithmic to be able to display the [8
+planets](http://news.bbc.co.uk/2/hi/5282440.stm) without having
+[Mercury](https://science.nasa.gov/mercury),
+[Venus](https://science.nasa.gov/venus/),
+[Earth](https://science.nasa.gov/earth/facts) and
+[Mars](https://science.nasa.gov/mars) squeezed around the
+[Sun](https://science.nasa.gov/sun/).
 
 The size is not proportional either.
 
+
 ### Bonus
 
 It also displays the position of 2 famous comets during their last approach:
 
-- The first one around the third IOCCC.
-- The second one between the thirteenth and fourteenth IOCCC.
+- The [first one](https://science.nasa.gov/solar-system/comets/1p-halley/)
+around the [third IOCCC](/years.html#1986).
+- The [second
+one](https://science.nasa.gov/solar-system/comets/c-1995-o1-hale-bopp/) between
+the [thirteenth](/years.html#1996) and [fourteenth](/years.html#1998) IOCCC.
+
 
 ### Limitations
 
 * ASCII character set is assumed.
 * A C99 compiler is required (for some `math.h` functions).
 * The position should be correct for years between (-1000; +3000)
-* The approximations done in the formula are OK for displaying the
-  position around the sun but not for other applications like ephemeride or
-  sky view from Earth (angles may be off by 1 or 2 degrees sometimes).
+* The approximations done in the formula are OK for displaying the position
+around the [Sun](https://science.nasa.gov/sun/) but not for other applications
+like [ephemeride](https://en.wikipedia.org/wiki/Ephemeris) or sky view from
+[Earth](https://science.nasa.gov/earth/facts) (angles may be off by 1 or 2
+degrees sometimes).
+
 
 ### Obfuscation
 
 * Reuse of 1 letter variables.
-* Only the main function with some `for` loops.
+* Only the `main()` function with some `for` loops.
 * Constants for orbital elements encoded in a string.
 * Hexadecimal and decimal values used inconsistently.
 * Comparisons order are not consistent.
-* A lot of stuff is done in the different parts of the for loop.
+* A lot of stuff is done in the different parts of the `for` loop.
+
 
 ### Compilation warnings
 
@@ -104,10 +122,10 @@ morgan1.c:56:14: warning: '&&' within '||' [-Wlogical-op-parentheses]
 This is due to most of the parentheses and braces being removed when
 unnecessary.
 
-To verify the display, you can look at one of this programs :
-* xephem : https://web.archive.org/web/20130310133219/http://www.clearskyinstitute.com/xephem/
-* homeplanet : https://www.fourmilab.ch/homeplanet/
-* https://www.theplanetstoday.com
+To verify the display, you can look at one of these programs :
+* xephem : <https://web.archive.org/web/20130310133219/http://www.clearskyinstitute.com/xephem/>
+* homeplanet : <https://www.fourmilab.ch/homeplanet/>
+* <https://www.theplanetstoday.com>
 
 
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