The literature values for the solubility product constant Ksp​ of calcium hydroxide Ca(OH)2​can vary slightly depending on the source and conditions of measurement. However, here are some commonly referenced values: 

1. CRC Handbook of Chemistry and Physics (97th Edition):

· Page: 5-36
· Author: John Rumble
· Ksp​ value: 5.02×10ˉ⁶ at 25°C

2. Chemical Principles by Peter Atkins and Loretta Jones:

· Page: 725
· Edition: 6th Edition
· Ksp​ value: 5.5×10ˉ⁶ at 25°C

3. Principles of General Chemistry by Martin Silberberg:

· Page: 737
· Edition: 3rd Edition
· Ksp​ value: 6.5×10ˉ⁶ at 25°C

4. Chemistry: The Molecular Nature of Matter and Change by Martin Silberberg and Patricia Amateis:

· Page: 925
· Edition: 8th Edition
· Ksp​ value: 5.5×10ˉ⁶ at 25°C

Remember, when citing such values, it's crucial to also consider the conditions under which the measurement was taken (e.g., temperature) and to ensure that the units are consistent. Additionally, newer editions of these references may have updated values or additional sources. Always verify with the most current and reputable sources available.