diff --git a/03_data/04_preprocessed_data/database_api_reference.pdf b/03_data/04_preprocessed_data/database_api_reference.pdf
deleted file mode 100644
index 984f223..0000000
Binary files a/03_data/04_preprocessed_data/database_api_reference.pdf and /dev/null differ
diff --git a/03_data/README.md b/03_data/README.md
index 7877b56..2ccd05d 100644
--- a/03_data/README.md
+++ b/03_data/README.md
@@ -18,6 +18,8 @@ These files show which variables have been collected in each wave.
   incorrect variable names were fixed and double entries from subjects who did a
   wave two or more times were removed; see `cleaning.R` and below for more
   details
+* `04_preprocessed_data` contains the preprocessed data files with scales
+  created from the items; see `database_api_reference.md` for a description of scales.
 
 ## Files
 
@@ -131,9 +133,10 @@ some cleaning.
 # Data preprocessing
 
 The final data preprocessing creates scales from the collected items. It was
-done in Python and the code for the preprocessing can be found in a separate
+done in Python, and the code for the preprocessing can be found in a separate
 code repository: https://gitea.iwm-tuebingen.de/HMC/preprocessing. The files
 with the final variables for each scale are then saved in the folder
-`03_data/04_preprocessed_data` as CSV files with file names
-`HMC_<wave>_preprocessed.csv`.
+`03_data/04_preprocessed_data`. Three versions are provided: csv, and excel 
+versions per wave as well as an overall sqlite database containing all waves in
+one file. `database_api_reference.md` contains the documentation of the database.
 
diff --git a/README.md b/README.md
index a764f00..edcccb9 100644
--- a/README.md
+++ b/README.md
@@ -76,12 +76,22 @@ The waves were collectec over the following dates:
  |   |   |-- HMC_wave5_cleaned.csv
  |   |   |-- HMC_wave6_cleaned.csv
  |   |-- 04_preprocessed_data
- |   |   |-- HMC_wave1_preprocessed.csv
- |   |   |-- HMC_wave2_preprocessed.csv
- |   |   |-- HMC_wave3_preprocessed.csv
- |   |   |-- HMC_wave4_preprocessed.csv
- |   |   |-- HMC_wave5_preprocessed.csv
- |   |   |-- HMC_wave6_preprocessed.csv
+ |   |   |-- csv
+ |   |   |   |-- HMC_wave1_preprocessed.csv
+ |   |   |   |-- HMC_wave2_preprocessed.csv
+ |   |   |   |-- HMC_wave3_preprocessed.csv
+ |   |   |   |-- HMC_wave4_preprocessed.csv
+ |   |   |   |-- HMC_wave5_preprocessed.csv
+ |   |   |   |-- HMC_wave6_preprocessed.csv
+ |   |   |-- excel
+ |   |   |   |-- HMC_wave1_preprocessed.xlsx
+ |   |   |   |-- HMC_wave2_preprocessed.xlsx
+ |   |   |   |-- HMC_wave3_preprocessed.xlsx
+ |   |   |   |-- HMC_wave4_preprocessed.xlsx
+ |   |   |   |-- HMC_wave5_preprocessed.xlsx
+ |   |   |   |-- HMC_wave6_preprocessed.xlsx
+ |   |   |-- database_api_reference.md
+ |   |   |-- hmc_data.sqlite
  |   |-- HMC_codebook.xlsx
  |   |-- item_reference.md
  |   |-- README.md