diff --git a/src/pricehist/outputs/ledger.py b/src/pricehist/outputs/ledger.py
index c030f9a..474d2ee 100644
--- a/src/pricehist/outputs/ledger.py
+++ b/src/pricehist/outputs/ledger.py
@@ -14,6 +14,23 @@ class Ledger(BaseOutput):
             lines.append(f"P {date} {fmt.time} {base} {quote_amount}")
         return "\n".join(lines) + "\n"
 
-    # TODO support additional details of the format:
     # https://www.ledger-cli.org/3.0/doc/ledger3.html#Commodities-and-Currencies
+    # > The commodity may be any non-numeric string that does not contain a
+    # > period, comma, forward slash or at-sign. It may appear before or after
+    # > the amount, although it is assumed that symbols appearing before the
+    # > amount refer to currencies, while non-joined symbols appearing after the
+    # > amount refer to commodities.
+
     # https://www.ledger-cli.org/3.0/doc/ledger3.html#Commoditized-Amounts
+    # > A commoditized amount is an integer amount which has an associated
+    # > commodity. This commodity can appear before or after the amount, and may
+    # > or may not be separated from it by a space. Most characters are allowed
+    # > in a commodity name, except for the following:
+    # > - Any kind of white-space
+    # > - Numerical digits
+    # > - Punctuation: .,;:?!
+    # > - Mathematical and logical operators: -+*/^&|=
+    # > - Bracketing characters: <>[](){}
+    # > - The at symbol: @
+    # > And yet, any of these may appear in a commodity name if it is
+    # > surrounded by double quotes