This book deals with the quantisation of topological quantum field theories in 1+1 space-time dimensions. These quantum eld theories are the Thirring model and the sine-Gordon model. The Thirring model is a fermionic quantum field theory, which is exactly solvable and hence an interesting laboratory to study quantum effects in a non-perturbative way. While it is well known that the massive Thirring model is renormalisable, the massless model was thought to be non-renormalisable. Here, a more general solution to the massless Thirring model is obtained, which allows to renormalise the massless...