diff --git a/docs/datadoc/documenting-a-resource.md b/docs/datadoc/documenting-a-resource.md
index e845a6d1..0ae55d9d 100644
--- a/docs/datadoc/documenting-a-resource.md
+++ b/docs/datadoc/documenting-a-resource.md
@@ -180,14 +180,15 @@ Ex: `distribution.downloadURL`.
 
 The header keyword(s) may be followed by an optional square bracket with the following syntax (inspired by URL options):
 
-    name[label?var1=value1&var2=value2]
+    name[label?key1=value1&key2=value2]
 
 where
-- `name`: is the column name that is mapped to a keyword (or set of dot-separated keywords) defined in the JSON-LD context.
+
+- `name`: is the column name that is mapped to a keyword (or set of dot-separated keywords) defined in the JSON-LD context. (_required_)
   The only formal requirement is that it cannot contain a begin brace ([), but it might be wise to be more strict.
 - `label`: is a label for the column.
   It is used to make the column unique or to group related columns.
-  The only formal requirement is that is cannot contain a question mark (?), but it is probably wise to be more strict.
+  The only formal requirement is that is cannot contain a question mark (?) or equal sign (=), but it is probably wise to be more strict.
   A digit should be allowed.
 - `key`: a key identifying an option for the column.
   Should be a valid C or Python identifier (regex: `[_a-zA-Z][_a-zA-Z0-9]*`).
@@ -195,6 +196,7 @@ where
   Should not contain (unescaped) ampersand (&) or end braces (]).
 
 Currently recognised keys:
+
 - **`unit`**: A unit symbol. All numbers in this column have this unit.
 - **`sep`**: Separator character. A common user request when you have multiple values for a column, is to be able to provide multiple values in a single cell, instead of duplicating the column. This option makes it possible to specify a separator character that can be used in this column.
 
@@ -216,16 +218,29 @@ Grouping of columns (e.g. for DLite datamodels):
 
 Specifying unit:
 
-| @id          | @type       | length[?unit=m] |
+| @id          | @type       | length[unit=m]  |
 |--------------|-------------|-----------------|
 | ex:my_length | emmo:Length | 3.2             |
 
 Specifying a separator:
 
-| @id       | @type        | keyword[?sep=;]    |
+| @id       | @type        | keyword[sep=;]     |
 |-----------|--------------|--------------------|
 | ex:mydata | emmo:Dataset | geology;stone;cave |
 
+Combining label ('temsample') and unit ('unit=mm'):
+
+| @id       | @type        | diameter[temsample?unit=mm] |
+|-----------|--------------|-----------------------------|
+| ex:mydata | emmo:Dataset | 3.0                         |
+
+Same as above, but with sample being a blank node (labeled 'temsample') with property `diameter` (with unit mm).
+In this case, we put the label on the `hasSample` property and the unit on the `diameter` property:
+
+| @id       | @type        | hasSample[temsample].diameter[unit=mm] |
+|-----------|--------------|----------------------------------------|
+| ex:mydata | emmo:Dataset | 3.0                                    |
+
 
 ### Complete example
 For example, the table
diff --git a/tests/datadoc/test_tabledoc.py b/tests/datadoc/test_tabledoc.py
index 5e8aee54..0d4a459b 100644
--- a/tests/datadoc/test_tabledoc.py
+++ b/tests/datadoc/test_tabledoc.py
@@ -388,12 +388,17 @@ def test_column():
     assert col5.options == {"sep": ",", "unit": "m"}
     assert col5.datatype is None
 
-    col6 = Column("creationDate", context=get_context())
-    assert col6.header == "creationDate"
-    assert col6.datatype == XSD.dateTime
+    col6 = Column("length[unit=m]")
+    assert col6.names == ["length"]
+    assert col6.label == ""
+    assert col6.options == {"unit": "m"}
 
+    col7 = Column("creationDate", context=get_context())
+    assert col7.header == "creationDate"
+    assert col7.datatype == XSD.dateTime
 
-def test_sep():
+
+def test_column_sep():
     """Test the column separation."""
 
     from tripper.datadoc import TableDoc
diff --git a/tripper/datadoc/tabledoc.py b/tripper/datadoc/tabledoc.py
index 1b01b1c6..8702064a 100644
--- a/tripper/datadoc/tabledoc.py
+++ b/tripper/datadoc/tabledoc.py
@@ -601,7 +601,7 @@ class Column:
     # pylint: disable=too-few-public-methods
 
     def __init__(self, header, context=None, strip=True):
-        # pylint: disable=line-too-long
+        # pylint: disable=line-too-long,too-many-branches
         """Initialise a column opject.
 
         Arguments:
@@ -623,10 +623,18 @@ def __init__(self, header, context=None, strip=True):
 
         label = fields[0][2].split("?", 1)[0]
         spec = fields[-1][2].split("?", 1)
+        opts = spec[1] if len(spec) == 2 else ""
+
+        # Special rule. If `label` contains an equal sign (=), it is treated
+        # to be the first part of `opts`.
+        # This allows the user to omit the ?-sign if there is no label, e.g.
+        # writing "length[unit=m]" instead of "length[?unit=m]"
+        if "=" in label:
+            label, opts = "", f"{label}&{opts}" if opts else label
 
         options = {}
-        if len(spec) == 2:
-            for opt in spec[1].split("&"):
+        if opts:
+            for opt in opts.split("&"):
                 k, v = opt.split("=", 1)
                 options[k] = v