Theory of Machine
The relation l = (2/3).(j + 2) apply only to kinematic chains in which lower pairs are used. This may be used to kinematic chains in which higher pairs are used, but each higher pair may be taken as equivalent to

Any one of these
Two lower pairs and two additional links
Two lower pairs and one additional link
One lower pair and two additional links

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Theory of Machine
Kinematic pairs are those which have

Point or line contact between the two elements when in motion
Surface contact between the two elements when in motion
Elements of pairs not held together mechanically
Two elements that permit relative motion

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