A New Reverse IIR Filtering Algorithm
Straight and time-reversed filters may be combined to form linear phase filters. Examples include a Linkwitz-Riley crossover and a Hilbert filter.
Matched Second Order Digital Filters
Biquad filters with magnitude response matching the analog counterpart for lowpass, bandpass, highpass, and peaking EQ prototypes.
A New Recursive Quadrature Oscillator
A recursive, stable, low-frequency accurate, equi-amplitude quadrature oscillator - the only one I am aware of which comprises these features.