Consider the following statements regarding governors:

1. A Wilson governor is a spring-controlled governor in which the vertical arms of the bell-crank lever are fitted with spring balls.

2. A Hartung governor is a spring-loaded type governor in which two bell-crank levers are pivoted at the ends of two arms which rotate with the spindle.

3. In a spring-controlled gravity governor, two bell-crank levers are pivoted on the moving sleeve.

4. In a Watt governor, a pair of balls (masses) is attached to a spindle with the help of links.

Which of the above statements are correct?