diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ebedc9c..1e6e6f6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1,4 +1,4 @@
-# Copyright 2021-2022 Andrey Semashev
+# Copyright 2021-2023 Andrey Semashev
 #
 # Distributed under the Boost Software License, Version 1.0.
 # (See accompanying file LICENSE_1_0.txt or copy at http://boost.org/LICENSE_1_0.txt)
@@ -33,16 +33,8 @@ jobs:
       matrix:
         include:
           # Linux, gcc
-          - toolset: gcc-4.4
-            cxxstd: "98,0x"
-            os: ubuntu-latest
-            container: ubuntu:16.04
-            install:
-              - g++-4.4
-            sources:
-              - "ppa:ubuntu-toolchain-r/test"
           - toolset: gcc-4.6
-            cxxstd: "03,0x"
+            cxxstd: "0x"
             os: ubuntu-latest
             container: ubuntu:16.04
             install:
@@ -50,70 +42,70 @@ jobs:
             sources:
               - "ppa:ubuntu-toolchain-r/test"
           - toolset: gcc-4.7
-            cxxstd: "03,11"
+            cxxstd: "11"
             os: ubuntu-latest
             container: ubuntu:16.04
             install:
               - g++-4.7
           - toolset: gcc-4.8
-            cxxstd: "03,11"
+            cxxstd: "11"
             os: ubuntu-latest
             container: ubuntu:18.04
             install:
               - g++-4.8
           - toolset: gcc-4.9
-            cxxstd: "03,11"
+            cxxstd: "11"
             os: ubuntu-latest
             container: ubuntu:16.04
             install:
               - g++-4.9
           - toolset: gcc-5
-            cxxstd: "03,11,14,1z"
+            cxxstd: "11,14,1z"
             os: ubuntu-latest
             container: ubuntu:16.04
             install:
               - g++-5
           - toolset: gcc-6
-            cxxstd: "03,11,14,1z"
+            cxxstd: "11,14,1z"
             os: ubuntu-latest
             container: ubuntu:18.04
             install:
               - g++-6
           - toolset: gcc-7
-            cxxstd: "03,11,14,17"
+            cxxstd: "11,14,17"
             os: ubuntu-latest
             container: ubuntu:18.04
             install:
               - g++-7
           - toolset: gcc-8
-            cxxstd: "03,11,14,17,2a"
+            cxxstd: "11,14,17,2a"
             os: ubuntu-latest
             container: ubuntu:18.04
             install:
               - g++-8
           - toolset: gcc-9
-            cxxstd: "03,11,14,17,2a"
+            cxxstd: "11,14,17,2a"
             os: ubuntu-20.04
             install:
               - g++-9
           - toolset: gcc-10
-            cxxstd: "03,11,14,17,20"
+            cxxstd: "11,14,17,20"
             os: ubuntu-20.04
             install:
               - g++-10
           - toolset: gcc-11
-            cxxstd: "03,11,14,17,20,23"
+            cxxstd: "11,14,17,20,23"
             os: ubuntu-22.04
             install:
               - g++-11
           - toolset: gcc-12
-            cxxstd: "03,11,14,17,20,23"
+            cxxstd: "11,14,17,20,23"
             os: ubuntu-22.04
             install:
               - g++-12
           - name: UBSAN
             toolset: gcc-11
-            cxxstd: "03,11,14,17,20,23"
+            cxxstd: "11,14,17,20,23"
             ubsan: 1
             build_variant: debug
             os: ubuntu-22.04
@@ -123,63 +115,63 @@ jobs:
           # Linux, clang
           - toolset: clang
             compiler: clang++-3.5
-            cxxstd: "03,11"
+            cxxstd: "11"
             os: ubuntu-latest
             container: ubuntu:16.04
             install:
               - clang-3.5
           - toolset: clang
             compiler: clang++-3.6
-            cxxstd: "03,11,14"
+            cxxstd: "11,14"
             os: ubuntu-latest
             container: ubuntu:16.04
             install:
               - clang-3.6
           - toolset: clang
             compiler: clang++-3.7
-            cxxstd: "03,11,14"
+            cxxstd: "11,14"
             os: ubuntu-latest
             container: ubuntu:16.04
             install:
               - clang-3.7
           - toolset: clang
             compiler: clang++-3.8
-            cxxstd: "03,11,14"
+            cxxstd: "11,14"
             os: ubuntu-latest
             container: ubuntu:16.04
             install:
               - clang-3.8
           - toolset: clang
             compiler: clang++-3.9
-            cxxstd: "03,11,14"
+            cxxstd: "11,14"
             os: ubuntu-latest
             container: ubuntu:18.04
             install:
               - clang-3.9
           - toolset: clang
             compiler: clang++-4.0
-            cxxstd: "03,11,14"
+            cxxstd: "11,14"
             os: ubuntu-latest
             container: ubuntu:18.04
             install:
               - clang-4.0
           - toolset: clang
             compiler: clang++-5.0
-            cxxstd: "03,11,14,1z"
+            cxxstd: "11,14,1z"
             os: ubuntu-latest
             container: ubuntu:18.04
             install:
               - clang-5.0
           - toolset: clang
             compiler: clang++-6.0
-            cxxstd: "03,11,14,17"
+            cxxstd: "11,14,17"
             os: ubuntu-latest
             container: ubuntu:18.04
             install:
               - clang-6.0
           - toolset: clang
             compiler: clang++-7
-            cxxstd: "03,11,14,17"
+            cxxstd: "11,14,17"
             os: ubuntu-latest
             container: ubuntu:18.04
             install:
@@ -187,7 +179,7 @@ jobs:
           # Note: clang-8 does not fully support C++20, so it is not compatible with libstdc++-8 in this mode
           - toolset: clang
             compiler: clang++-8
-            cxxstd: "03,11,14,17,2a"
+            cxxstd: "11,14,17,2a"
             os: ubuntu-latest
             container: ubuntu:18.04
             install:
@@ -196,49 +188,57 @@ jobs:
             gcc_toolchain: 7
           - toolset: clang
             compiler: clang++-9
-            cxxstd: "03,11,14,17,2a"
+            cxxstd: "11,14,17,2a"
             os: ubuntu-20.04
             install:
               - clang-9
           - toolset: clang
             compiler: clang++-10
-            cxxstd: "03,11,14,17,20"
+            cxxstd: "11,14,17,20"
             os: ubuntu-20.04
             install:
               - clang-10
           - toolset: clang
             compiler: clang++-11
-            cxxstd: "03,11,14,17,20"
+            cxxstd: "11,14,17,20"
             os: ubuntu-22.04
             install:
               - clang-11
           - toolset: clang
             compiler: clang++-12
-            cxxstd: "03,11,14,17,20,2b"
+            cxxstd: "11,14,17,20,2b"
             os: ubuntu-22.04
             install:
               - clang-12
+              - g++-11
+            gcc_toolchain: 11
           - toolset: clang
             compiler: clang++-13
-            cxxstd: "03,11,14,17,20,2b"
+            cxxstd: "11,14,17,20,2b"
             os: ubuntu-22.04
             install:
               - clang-13
+              - g++-11
+            gcc_toolchain: 11
           - toolset: clang
             compiler: clang++-14
-            cxxstd: "03,11,14,17,20,2b"
+            cxxstd: "11,14,17,20,2b"
             os: ubuntu-22.04
             install:
               - clang-14
+              - g++-11
+            gcc_toolchain: 11
           - toolset: clang
             compiler: clang++-15
-            cxxstd: "03,11,14,17,20,2b"
+            cxxstd: "11,14,17,20,2b"
             os: ubuntu-22.04
             install:
               - clang-15
+              - g++-11
+            gcc_toolchain: 11
           - toolset: clang
             compiler: clang++-16
-            cxxstd: "03,11,14,17,20,2b"
+            cxxstd: "11,14,17,20,2b"
             os: ubuntu-22.04
             install:
               - clang-16
@@ -248,7 +248,7 @@ jobs:
               - "https://apt.llvm.org/llvm-snapshot.gpg.key"
           - toolset: clang
             compiler: clang++-16
-            cxxstd: "03,11,14,17,20,2b"
+            cxxstd: "11,14,17,20,2b"
             os: ubuntu-22.04
             install:
               - clang-16
@@ -263,7 +263,7 @@ jobs:
           - name: UBSAN
             toolset: clang
             compiler: clang++-15
-            cxxstd: "03,11,14,17,20,2b"
+            cxxstd: "11,14,17,20,2b"
             cxxflags: -stdlib=libc++
             linkflags: -stdlib=libc++
             ubsan: 1
@@ -275,7 +275,7 @@ jobs:
               - libc++abi-15-dev
 
           - toolset: clang
-            cxxstd: "03,11,14,17,2a"
+            cxxstd: "11,14,17,2a"
             os: macos-11
 
     timeout-minutes: 60
@@ -499,7 +499,7 @@ jobs:
             addrmd: 32,64
             os: windows-2022
           - toolset: gcc
-            cxxstd: "03,11,14,17,2a"
+            cxxstd: "11,14,17,2a"
             addrmd: 64
             os: windows-2019