Theory of Machine
The Grubler's criterion for determining the degrees of freedom (n) of a mechanism having plane motion is (where l = Number of links, and j = Number of binary joints)

n = 3(l - 1) - 2j
n = 2(l - 1) - 2j
n = (l -1) - j
n = 4(l - 1) - 3j

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Theory of Machine
Oldham's coupling is the

Second inversion of double slider crank chain
Third inversion of double slider crank chain
Third inversion of slider crank chain
Second inversion of single slider crank chain

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