Wind Correction Angle: true or magnetic wind direction?

There is a section on winds on Ed Williams' "Aviation Formulary" page which provides various formulae to find wind correction angle (WCA). One of the variables used is wind direction (from).

I know that usually the direction of winds aloft is given in true degrees while the surface winds are given in magnetic to help pilots determine the proper runway. However, I couldn't understand which wind direction (true or magnetic) Ed uses for his WCA formulae. E.g., in this particular example showing calculation of head-/tailwind components I guess the wind direction value is in magnetic degrees since the problem is tackling surface winds on runway 3:

Example: Wind 060 @ 20 departing Runway 3.

 

WS=20 knots

WD=60 degrees = 60*pi/180 radians           <<-- what is this: true or magnetic wind direction?!

RD=30 degrees = 30*pi/180 radians
Plugging in:
Headwind=17.32 knots
Crosswind = 10 knots (from right)

But what about winds aloft for calculating WCA? I'm particularly concerned about wind direction degrees in this formula: 

WCA = atan2(wind speed * SIN(heading - wind direction), true airspeed - wind speed * COS(heading - wind direction))

I will be grateful if anyone can enlighten me on this issue!!!

Thanks!