There are a various links where open access (free download) available related to aldol reaction/condensation.
- Aldol condensation - Springer
- Chapter 17, Aldehydes and Ketones II: Aldol Reactions
- A Double Aldol Condensation
- The Selective Aldol Reaction
- Crossed Aldol Condensation
- Solvent-Free Aldol
- Aldol Condensation