see JANA2006/2020 software and the papers published by the authors of the software.

Here are a few examples:

• "Modulated Structures in Organometallics" by G. R. Mitchell, A. L. Goodwin, and D. J. Powell. This book provides a comprehensive overview of the topic, including the history of modulated structures in organometallics, the different types of modulation, and their physical properties.
• "Modulated Structures in Inorganic and Organometallic Compounds" by G. R. Mitchell and D. J. Powell. This book provides a more in-depth coverage of the topic, including a detailed discussion of the different types of modulation, the physical properties of modulated structures, and their applications in materials science and catalysis.
• "Modulated structures in inorganic and organometallic compounds: a review" by G. R. Mitchell, D. J. Powell, and A. L. Goodwin. This review paper provides a broad overview of the topic, including the different types of modulation, the physical properties of modulated structures, and their applications in materials science, catalysis, and electronics.

There are several software packages that can be used for data reduction of X-ray and neutron diffraction data, and for the refinement of modulated crystal structures. example:

• FullProf Suite: A software package for the analysis of powder diffraction data. It can be used for the refinement of modulated crystal structures, including commensurate and incommensurate modulations.
• Topas: A software package for the analysis of X-ray and neutron diffraction data. It can be used for the refinement of modulated crystal structures, including commensurate and incommensurate modulations.
• FullProf-Win: A Windows version of the FullProf Suite. It can be used for the refinement of modulated crystal structures, including commensurate and incommensurate modulations.
• VESTA: A software package for the visualization of crystal structures. It can be used to view and analyze the crystal structures of modulated compounds.
• Topas Academic: is a user-friendly software package for the analysis of X-ray and neutron diffraction data and it is also a good option for refinement of modulated crystal structures.

It's worth noting that most of the software packages are available for free, however, some of them have a commercial version with more advanced features. It's important to check the system requirements and the level of knowledge needed to use the software before deciding which one to use.

softwares like apex and olex 2 could be used for data reduction and structure solution and refinements. Also papers from these authors could be sued for better understanding. besides that there are YouTube videos as helping materials by olex authors.