diff --git a/notes.md b/notes.md
index 6b3afe6..de28a60 100644
--- a/notes.md
+++ b/notes.md
@@ -402,6 +402,10 @@ see Screening Tool document for exact keywords used during screening.
 
 ## Matrix extraction properties
 
+For up-to-date usage of extraction keys please see `extraction_template.yml` in data directory.
+Information kept here for full-text descriptions of each option, to be migrated
+to extraction metadata sheet.
+
 | Publication info | Description                                  |
 | ---              | ---                                          |
 | author           |                                              |
@@ -443,6 +447,7 @@ see Screening Tool document for exact keywords used during screening.
 | study_method       | What is the main method of the study? (list:txt)                                                                    |
 | indicator_relative | Is the main indicator used relative or absolute? (0: absolute, 1: relative)                                         |
 | sample_size        | What is the main sample size/observation number of the study? (numeric)                                             |
+| sample_unit        | What is the main sample unit (person,household,firm, ...)? (txt)                                             |
 | representativeness | At what level is the study mainly representative? (national, subnational, rural, urban..) (list:txt)                |
 | direction          | What is the main direction of relation between independent/dependent variables? (0: negative, 1: positive)          |
 | significance       | What is the main level of statistical significance? (2: significant, 1: marginally significant, 0: non significant) |