Every invertible matrix can be written as the exponential of one other matrix I'm looking for a proof of this claim: "every invertible matrix can be written as the exponential of another matrix". 
I'm not familiar yet with logarithms of matrices, so I wonder if a proof exists, without them. I'll be happy with any proof anyways. I hope someone can help.

see this book on the net, it can be helpful
Miroslav Fiedler, Special Matrices and Their Applications in Numerical Mathematics, Springer (1986) 
