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Published online by Cambridge University Press: 14 August 2015
Recent results with the slitless spectrum technique are reviewed and the total surface densities from five independent surveys are compared. The observational base for extending the technique to search for quasars with z > 3.5 is now large enough that either the apparent cutoff at z = 3.5 will be confirmed in new surveys or quasars with z > 3.5 will be found.