diff --git a/stix2/pattern_visitor.py b/stix2/pattern_visitor.py
index f947437..a891e12 100644
--- a/stix2/pattern_visitor.py
+++ b/stix2/pattern_visitor.py
@@ -3,7 +3,6 @@ import inspect
 
 from stix2patterns.exceptions import ParseException
 from stix2patterns.grammars.STIXPatternParser import TerminalNode
-from stix2patterns.grammars.STIXPatternVisitor import STIXPatternVisitor
 from stix2patterns.v20.grammars.STIXPatternParser import \
     STIXPatternParser as STIXPatternParser20
 from stix2patterns.v20.grammars.STIXPatternVisitor import \
@@ -102,7 +101,10 @@ class STIXPatternVisitorForSTIX2():
     # Visit a parse tree produced by STIXPatternParser#observationExpressionCompound.
     def visitObservationExpressionCompound(self, ctx):
         children = self.visitChildren(ctx)
-        return self.instantiate("ObservationExpression", children[1])
+        if isinstance(children[0], TerminalNode) and children[0].symbol.type == self.parser_class.LPAREN:
+            return self.instantiate("ParentheticalExpression", children[1])
+        else:
+            return self.instantiate("ObservationExpression", children[0])
 
     # Visit a parse tree produced by STIXPatternParser#observationExpressionWithin.
     def visitObservationExpressionWithin(self, ctx):
diff --git a/stix2/patterns.py b/stix2/patterns.py
index 2e149be..f0cceb8 100644
--- a/stix2/patterns.py
+++ b/stix2/patterns.py
@@ -551,7 +551,7 @@ class ObservationExpression(_PatternExpression):
         self.operand = operand
 
     def __str__(self):
-        return "[%s]" % self.operand
+        return "%s" % self.operand if isinstance(self.operand, (ObservationExpression, _CompoundObservationExpression)) else "[%s]" % self.operand
 
 
 class _CompoundObservationExpression(_PatternExpression):
diff --git a/stix2/test/v21/test_pattern_expressions.py b/stix2/test/v21/test_pattern_expressions.py
index 804e88c..f176db7 100644
--- a/stix2/test/v21/test_pattern_expressions.py
+++ b/stix2/test/v21/test_pattern_expressions.py
@@ -216,6 +216,31 @@ def test_parsing_less_than_or_equal():
     assert str(patt_obj) == "[file:size <= 1024]"
 
 
+def test_parsing_issubset():
+    patt_obj = create_pattern_object("[network-traffic:dst_ref.value ISSUBSET '2001:0db8:dead:beef:0000:0000:0000:0000/64']")
+    assert str(patt_obj) == "[network-traffic:dst_ref.value ISSUBSET '2001:0db8:dead:beef:0000:0000:0000:0000/64']"
+
+
+def test_parsing_issuperset():
+    patt_obj = create_pattern_object("[network-traffic:dst_ref.value ISSUPERSET '2001:0db8:dead:beef:0000:0000:0000:0000/64']")
+    assert str(patt_obj) == "[network-traffic:dst_ref.value ISSUPERSET '2001:0db8:dead:beef:0000:0000:0000:0000/64']"
+
+
+def test_parsing_like():
+    patt_obj = create_pattern_object("[directory:path LIKE 'C:\\\\Windows\\\\%\\\\foo']")
+    assert str(patt_obj) == "[directory:path LIKE 'C:\\\\Windows\\\\%\\\\foo']"
+
+
+def test_parsing_match():
+    patt_obj = create_pattern_object("[process:command_line MATCHES '^.+>-add GlobalSign.cer -c -s -r localMachine Root$'] FOLLOWEDBY [process:command_line MATCHES '^.+>-add GlobalSign.cer -c -s -r localMachineTrustedPublisher$'] WITHIN 300 SECONDS")  # noqa
+    assert str(patt_obj) == "[process:command_line MATCHES '^.+>-add GlobalSign.cer -c -s -r localMachine Root$'] FOLLOWEDBY [process:command_line MATCHES '^.+>-add GlobalSign.cer -c -s -r localMachineTrustedPublisher$'] WITHIN 300 SECONDS"
+
+
+def test_parsing_followed_by():
+    patt_obj = create_pattern_object("([file:hashes.MD5 = '79054025255fb1a26e4bc422aef54eb4'] FOLLOWEDBY [windows-registry-key:key = 'HKEY_LOCAL_MACHINE\\\\foo\\\\bar']) WITHIN 300 SECONDS")  # noqa
+    assert str(patt_obj) == "([file:hashes.MD5 = '79054025255fb1a26e4bc422aef54eb4'] FOLLOWEDBY [windows-registry-key:key = 'HKEY_LOCAL_MACHINE\\\\foo\\\\bar']) WITHIN 300 SECONDS"  # noqa
+
+
 def test_not():
     exp = stix2.LessThanComparisonExpression(
         "file:size",