This work would not be possible without the efforts of:

CURRAH μSPEECH programming manual (1983)

https://maziac.github.io/currah_uspeech_tests/data/currah_manual.pdf

General Instrument SP0256-AL2 datasheet

https://bitsavers.org/components/gi/speech/General_Instrument_-_SP0256A-AL2_datasheet_(Radio_Shack_276-1784)_-_Apr1984.pdf

SkoolKit Spectrum ROM disassembly

https://skoolkit.ca/disassemblies/rom/

maziac — currah_uspeech_tests

https://github.com/maziac/currah_uspeech_tests (maziac thanks Kio (Günter Woigk))

Spectrum Computing — Currah MicroSpeech

https://spectrumcomputing.co.uk/entry/1000081/Hardware/Currah_MicroSpeech

CPCWiki — SP0256 allophone list and chip recordings

https://www.cpcwiki.eu/index.php/SP0256_Allophones

ExtremeElectronics — packed AL2 PCM samples

https://github.com/ExtremeElectronics/RC2040

Kio (Günter Woigk) — Currah μSpeech hardware notes

https://k1.spdns.de/Vintage/Sinclair/82/Peripherals/Currah%20uSpeech/

MAME — uspeech.cpp

https://github.com/mamedev/mame/blob/master/src/devices/bus/spectrum/uspeech.cpp

archive.org OCR text of the original manual (Mark Anson, 1983)

https://archive.org/stream/currahuspeech/Currah_uSPEECH_djvu.txt

Fuse emulator uspeech patch #142

https://sourceforge.net/p/fuse-emulator/patches/142/

SZX uspeech block

https://www.spectaculator.com/docs/zx-state/uspeech.html

These pages were a great help when working out the paging, the allophone set and the BASIC interface.

Period reviews and features indexed on Spectrum Computing include Sinclair User #21 (Dec 1983) p.40; Your Spectrum #1 (Jan 1984) p.33 and #9 (Nov 1984) p.52; Personal Computer News #34 (2 Nov 1983) p.39, #40 (14 Dec 1983) supplement "PCN Micropaedia v13 part 2: Peripherals" p.321, and #49 (18 Feb 1984) p.36; C&VG #28 (Feb 1984) p.156; ZX Computing #14 (Aug 1984) p.33 and #17 (Feb 1985) p.115; Sinclair User Annual 1984 p.39; Crash v1 #1 (Feb 1984) p.26 and v1 #2 (Mar 1984) p.42; and Computer Choice (Apr 1984) p.34.