Välimäki, Vesa (1995 թ․ հունվարի 1). «Discrete-time modeling of acoustic tubes using fractional delay filters»(PDF) (English). Otaniemi: Helsinki University of Technology. «Thiran (1971) proposed an analytic solution for the coefficients of an all-pole low-pass filter with a maximally flat group delay ... it seems that the result of Thiran is better suited to the design of allpass than all-pole filters.» {{cite journal}}: Cite journal requires |journal= (օգնություն)CS1 սպաս․ չճանաչված լեզու (link)
Madisetti, Vijay (1997 թ․ դեկտեմբերի 29). «Section 11.3.2.2 Classical IIR Filter Types». The Digital Signal Processing Handbook (անգլերեն). CRC Press. էջ 282. ISBN9780849385728. «A fifth IIR filter ... is the all-pole filter that possesses a maximally flat group delay ... It should be noted that this filter is not obtained directly from the analog equivalent, the Bessel filter ... Instead, it can be derived directly in the digital domain [Thiran]»
