David Weisburd, Charlotte Gill, Block Randomized Trials at Places: Rethinking the Limitations of Small N Experiments, Journal of Quantitative Criminology, Vol. 30, No. 1 (March 2014), pp. 97-112 ...

However, stratified permuted block randomization fails to achieve good overall balance when the number of strata is large, whereas traditional minimization methods also suffer from the potential ...