diff --git a/test/test_unit_strings.cpp b/test/test_unit_strings.cpp
index 8ea92b4e..3d1fc924 100644
--- a/test/test_unit_strings.cpp
+++ b/test/test_unit_strings.cpp
@@ -944,6 +944,11 @@ TEST(stringToUnits, equivalents4)
             "nanomole of (1/2) cystine per milligram of protein")));
 }
 
+TEST(stringToUnits, commodityConsiderations)
+{
+    auto ut = unit_from_string("mile(USA){\\{}");
+    EXPECT_NE(ut.commodity(), 0U);
+}
 TEST(stringToUnits, electronVolt)
 {
     EXPECT_EQ(unit_from_string("eV"), precise::energy::eV);
@@ -1166,9 +1171,34 @@ TEST(stringToUnit, handlingOfSquared)
     auto u2 = unit_from_string("pascal squared second");
     EXPECT_EQ(u2, precise::Pa.pow(2) * precise::s);
 
+    auto u2b = unit_from_string("pascal squared per second squared");
+    EXPECT_EQ(u2b, precise::Pa.pow(2) / precise::s.pow(2));
+
+    auto u2c = unit_from_string("pascal squared per second squared per kg");
+    EXPECT_EQ(u2c, precise::Pa.pow(2) / precise::s.pow(2) / precise::kg);
+
+    auto u2d = unit_from_string("pascal cubed second");
+    EXPECT_EQ(u2d, precise::Pa.pow(3) * precise::s);
+
+    auto u2e = unit_from_string("pascal cubed per second cubed");
+    EXPECT_EQ(u2e, precise::Pa.pow(3) / precise::s.pow(3));
+
+    auto u2f = unit_from_string("pascal squared per second squared per kg");
+    EXPECT_EQ(u2f, precise::Pa.pow(2) / precise::s.pow(2) / precise::kg);
+
+    auto u2g = unit_from_string("pascal squared / second squared / kg");
+    EXPECT_EQ(u2g, precise::Pa.pow(2) / precise::s.pow(2) / precise::kg);
+
     auto u3 = unit_from_string("coulomb metre squared per volt");
     EXPECT_EQ(u3, precise::C * precise::m.pow(2) / precise::V);
 
+    auto u3v = unit_from_string(
+        "kg per coulomb metre squared per second squared per volt");
+    EXPECT_EQ(
+        u3v,
+        precise::kg / (precise::C * precise::m.pow(2)) / precise::V /
+            precise::s.pow(2));
+
     auto u4 = unit_from_string("ampere square metre per joule second");
     EXPECT_EQ(u4, precise::A * precise::m.pow(2) / (precise::J * precise::s));
 
@@ -1216,6 +1246,21 @@ TEST(stringToUnits, modifiedStrings)
     EXPECT_EQ(u8, unit_from_string("[QT_US]"));
 }
 
+TEST(stringToUnits, tempString)
+{
+    auto u4 = unit_from_string("calorie (20 degC)");
+    EXPECT_EQ(u4, precise::energy::cal_20);
+
+    u4 = unit_from_string("calorie 20C");
+    EXPECT_EQ(u4, precise::energy::cal_20);
+
+    u4 = unit_from_string("calorie at 20C");
+    EXPECT_EQ(u4, precise::energy::cal_20);
+
+    u4 = unit_from_string("calorie_20C");
+    EXPECT_EQ(u4, precise::energy::cal_20);
+}
+
 TEST(stringToUnits, addition)
 {
     auto u1 = unit_from_string("cm+cm");
diff --git a/units/units.cpp b/units/units.cpp
index 224ab52a..c4d2e061 100644
--- a/units/units.cpp
+++ b/units/units.cpp
@@ -2709,11 +2709,6 @@ bool bracketModifiers(std::string& unit_string)
 
                 unit_string.replace(ploc + 1, cloc - ploc, modloc->second);
                 unit_string[ploc] = '_';
-                if (unit_string[ploc - 1] == ' ') {
-                    unit_string.erase(ploc - 1, 1);
-                    --ploc;
-                }
-
                 modified = true;
             }
             ploc = unit_string.find_first_of(seg[0], ploc + 1);
@@ -3533,9 +3528,13 @@ static bool isolatePriorModifier(
     auto modfind = unit_string.find(modifier);
     if (modfind != std::string::npos) {
         auto offset = modfind + modifier.size();
+        // LCOV_EXCL_START
+        // this condition is not used in current use cases but it is dangerous
+        // to make assumptions that will always be the case
         if (modifier.back() != ' ') {
             ++offset;
         }
+        // LCOV_EXCL_STOP
         auto kloc = unit_string.find_first_not_of(' ', offset);
         if (kloc != std::string::npos &&
             (unit_string[kloc] == check1 || unit_string[kloc] == check2)) {
@@ -4743,22 +4742,25 @@ static bool cleanUnitString(std::string& unit_string, std::uint64_t match_flags)
     return (changed || unit_string.size() != slen);
 }
 
-static void modifyTailCodes(std::string& unit_string)
+static bool modifyTailCodes(std::string& unit_string)
 {
     if (!unit_string.empty() &&
         (unit_string.back() == 'F' || unit_string.back() == 'C')) {
-        static UNITS_CPP14_CONSTEXPR_OBJECT std::array<ckpair, 10>
+        static UNITS_CPP14_CONSTEXPR_OBJECT std::array<ckpair, 12>
             trailTempCodeReplacements{{
                 ckpair{"at39F", "[39]"},
                 ckpair{"39F", "[39]"},
                 ckpair{"at60F", "[60]"},
                 ckpair{"60F", "[60]"},
-                ckpair{"at0C", "[00]"},
-                ckpair{"0C", "[00]"},
+                ckpair{"at20C", "[20]"},
+                ckpair{"20C", "[20]"},
                 ckpair{"at23C", "[23]"},
                 ckpair{"23C", "[23]"},
                 ckpair{"at4C", "[04]"},
                 ckpair{"4C", "[04]"},
+                ckpair{"at0C", "[00]"},
+                ckpair{"0C", "[00]"},
+
             }};
 
         for (const auto& endTemp : trailTempCodeReplacements) {
@@ -4769,9 +4771,11 @@ static void modifyTailCodes(std::string& unit_string)
                 if (unit_string[unit_string.size() - 5] != '_') {
                     unit_string.insert(unit_string.size() - 4, 1, '_');
                 }
+                return true;
             }
         }
     }
+    return false;
 }
 
 /// cleanup phase 2 if things still aren't working
@@ -5690,7 +5694,12 @@ static precise_unit unit_from_string_internal(
         }
     }
 
-    modifyTailCodes(unit_string);
+    if (modifyTailCodes(unit_string)) {
+        retunit = get_unit(unit_string, match_flags);
+        if (!is_error(retunit)) {
+            return retunit;
+        }
+    }
 
     if (!containsPer) {
         retunit = checkMultiplierCharacter(unit_string, match_flags, '-');