diff --git a/internal/field/field.go b/internal/field/field.go
index 0d22e2a33..eafca7335 100644
--- a/internal/field/field.go
+++ b/internal/field/field.go
@@ -431,9 +431,7 @@ func CoordNameForExtensionDegree(degree uint8) string {
 }
 
 func (f *FieldConfig) WriteElement(element Element) string {
-	builder := bavard.StringBuilderPool.Get().(*strings.Builder)
-	builder.Reset()
-	defer bavard.StringBuilderPool.Put(builder)
+	var builder strings.Builder
 
 	builder.WriteString("{")
 	length := len(element)
@@ -449,7 +447,7 @@ func (f *FieldConfig) WriteElement(element Element) string {
 			builder.WriteString(": fp.Element{")
 		}
 		mont := f.ToMont(e)
-		bavard.WriteBigIntAsUint64Slice(builder, &mont)
+		bavard.WriteBigIntAsUint64Slice(&builder, &mont)
 		if length > 1 {
 			builder.WriteString("},\n")
 		}
diff --git a/utils/supsub.go b/utils/supsub.go
new file mode 100644
index 000000000..759d4e394
--- /dev/null
+++ b/utils/supsub.go
@@ -0,0 +1,251 @@
+package utils
+
+import (
+	"bytes"
+	"fmt"
+)
+
+// The following is taken from https://github.com/lynn9388/supsub
+// developed by lynn9388@gmail.com under Apache 2.0.
+// It provides a mapping from normal unicode text to superscript
+// and subscript.
+
+var superscripts = map[rune]rune{
+	// Superscripts - Superscripts and Subscripts
+	// https://www.unicode.org/charts/PDF/U2070.pdf
+	'\u0030': '\u2070',
+	'\u0069': '\u2071',
+	'\u0034': '\u2074',
+	'\u0035': '\u2075',
+	'\u0036': '\u2076',
+	'\u0037': '\u2077',
+	'\u0038': '\u2078',
+	'\u0039': '\u2079',
+	'\u002b': '\u207a',
+	'\u2212': '\u207b',
+	'\u003d': '\u207c',
+	'\u0028': '\u207d',
+	'\u0029': '\u207e',
+	'\u006e': '\u207f',
+
+	// Latin superscript modifier letters - Spacing Modifier Letters
+	// https://www.unicode.org/charts/PDF/U02B0.pdf
+	'\u0068': '\u02b0',
+	'\u0266': '\u02b1',
+	'\u006a': '\u02b2',
+	'\u0072': '\u02b3',
+	'\u0279': '\u02b4',
+	'\u027b': '\u02b5',
+	'\u0281': '\u02b6',
+	'\u0077': '\u02b7',
+	'\u0079': '\u02b8',
+
+	// Additions based on 1989 IPA - Spacing Modifier Letters
+	// https://www.unicode.org/charts/PDF/U02B0.pdf
+	'\u0263': '\u02e0',
+	'\u006c': '\u02e1',
+	'\u0073': '\u02e2',
+	'\u0078': '\u02e3',
+	'\u0295': '\u02e4',
+
+	// Latin superscript modifier letters - Phonetic Extensions
+	// https://www.unicode.org/charts/PDF/U1D00.pdf
+	'\u0041': '\u1d2c',
+	'\u00c6': '\u1d2d',
+	'\u0042': '\u1d2e',
+	'\u0044': '\u1d30',
+	'\u0045': '\u1d31',
+	'\u018e': '\u1d32',
+	'\u0047': '\u1d33',
+	'\u0048': '\u1d34',
+	'\u0049': '\u1d35',
+	'\u004a': '\u1d36',
+	'\u004b': '\u1d37',
+	'\u004c': '\u1d38',
+	'\u004d': '\u1d39',
+	'\u004e': '\u1d3a',
+	'\u004f': '\u1d3c',
+	'\u0222': '\u1d3d',
+	'\u0050': '\u1d3e',
+	'\u0052': '\u1d3f',
+	'\u0054': '\u1d40',
+	'\u0055': '\u1d41',
+	'\u0057': '\u1d42',
+	'\u0061': '\u1d43', // '\u0061'(a) '\u1d43'(ᵃ) '\u00aa'(ª)
+	'\u0250': '\u1d44',
+	'\u0251': '\u1d45',
+	'\u1d02': '\u1d46',
+	'\u0062': '\u1d47',
+	'\u0064': '\u1d48',
+	'\u0065': '\u1d49',
+	'\u0259': '\u1d4a',
+	'\u025b': '\u1d4b',
+	'\u1d08': '\u1d4c',
+	'\u0067': '\u1d4d',
+	'\u006b': '\u1d4f',
+	'\u006d': '\u1d50',
+	'\u014b': '\u1d51',
+	'\u006f': '\u1d52', // '\u006f'(o) '\u1d52'(ᵒ) '\u00ba'(º)
+	'\u0254': '\u1d53',
+	'\u1d16': '\u1d54',
+	'\u1d17': '\u1d55',
+	'\u0070': '\u1d56',
+	'\u0074': '\u1d57',
+	'\u0075': '\u1d58',
+	'\u1d1d': '\u1d59',
+	'\u026f': '\u1d5a',
+	'\u0076': '\u1d5b',
+	'\u1d25': '\u1d5c',
+
+	// Greek superscript modifier letters - Phonetic Extensions
+	// https://www.unicode.org/charts/PDF/U1D00.pdf
+	'\u03b2': '\u1d5d',
+	'\u03b3': '\u1d5e',
+	'\u03b4': '\u1d5f',
+	'\u03c6': '\u1d60',
+	'\u03c7': '\u1d61',
+
+	// Caucasian linguistics - Phonetic Extensions
+	// https://www.unicode.org/charts/PDF/U1D00.pdf
+	'\u043d': '\u1d78',
+
+	// Modifier letters - Phonetic Extensions Supplement
+	// https://www.unicode.org/charts/PDF/U1D80.pdf
+	'\u0252': '\u1d9b',
+	'\u0063': '\u1d9c',
+	'\u0255': '\u1d9d',
+	'\u00f0': '\u1d9e',
+	'\u025c': '\u1d9f',
+	'\u0066': '\u1da0',
+	'\u025f': '\u1da1',
+	'\u0261': '\u1da2',
+	'\u0265': '\u1da3',
+	'\u0268': '\u1da4',
+	'\u0269': '\u1da5',
+	'\u026a': '\u1da6',
+	'\u1d7b': '\u1da7',
+	'\u029d': '\u1da8',
+	'\u026d': '\u1da9',
+	'\u1d85': '\u1daa',
+	'\u029f': '\u1dab',
+	'\u0271': '\u1dac',
+	'\u0270': '\u1dad',
+	'\u0272': '\u1dae',
+	'\u0273': '\u1daf',
+	'\u0274': '\u1db0',
+	'\u0275': '\u1db1',
+	'\u0278': '\u1db2',
+	'\u0282': '\u1db3',
+	'\u0283': '\u1db4',
+	'\u01ab': '\u1db5',
+	'\u0289': '\u1db6',
+	'\u028a': '\u1db7',
+	'\u1d1c': '\u1db8',
+	'\u028b': '\u1db9',
+	'\u028c': '\u1dba',
+	'\u007a': '\u1dbb',
+	'\u0290': '\u1dbc',
+	'\u0291': '\u1dbd',
+	'\u0292': '\u1dbe',
+	'\u03b8': '\u1dbf',
+
+	// Latin-1 punctuation and symbols - C1 Controls and Latin-1 Supplement
+	// https://www.unicode.org/charts/PDF/U0080.pdf
+	//'\u0061': '\u00aa', // '\u0061'(a) '\u1d43'(ᵃ) '\u00aa'(ª)
+	'\u0032': '\u00b2',
+	'\u0033': '\u00b3',
+	'\u0031': '\u00b9',
+	//'\u006f': '\u00ba', // '\u006f'(o) '\u1d52'(ᵒ) '\u00ba'(º)
+}
+var subscripts = map[rune]rune{
+	// Subscripts - Superscripts and Subscripts
+	// https://www.unicode.org/charts/PDF/U2070.pdf
+	'\u0030': '\u2080',
+	'\u0031': '\u2081',
+	'\u0032': '\u2082',
+	'\u0033': '\u2083',
+	'\u0034': '\u2084',
+	'\u0035': '\u2085',
+	'\u0036': '\u2086',
+	'\u0037': '\u2087',
+	'\u0038': '\u2088',
+	'\u0039': '\u2089',
+	'\u002b': '\u208a',
+	'\u2212': '\u208b',
+	'\u003d': '\u208c',
+	'\u0028': '\u208d',
+	'\u0029': '\u208e',
+	'\u0061': '\u2090',
+	'\u0065': '\u2091',
+	'\u006f': '\u2092',
+	'\u0078': '\u2093',
+	'\u0259': '\u2094',
+
+	// Subscripts for UPA - Superscripts and Subscripts
+	// https://www.unicode.org/charts/PDF/U2070.pdf
+	'\u0068': '\u2095',
+	'\u006b': '\u2096',
+	'\u006c': '\u2097',
+	'\u006d': '\u2098',
+	'\u006e': '\u2099',
+	'\u0070': '\u209a',
+	'\u0073': '\u209b',
+	'\u0074': '\u209c',
+
+	// Latin subscript modifier letters - Phonetic Extensions
+	// https://www.unicode.org/charts/PDF/U1D00.pdf
+	'\u0069': '\u1d62',
+	'\u0072': '\u1d63',
+	'\u0075': '\u1d64',
+	'\u0076': '\u1d65',
+
+	// Greek subscript modifier letters - Phonetic Extensions
+	// https://www.unicode.org/charts/PDF/U1D00.pdf
+	'\u03b2': '\u1d66',
+	'\u03b3': '\u1d67',
+	'\u03c1': '\u1d68',
+	'\u03c6': '\u1d69',
+	'\u03c7': '\u1d6a',
+}
+
+// sup converts a rune to superscript. It returns the superscript or the
+// original rune and a error if there is no corresponding superscript.
+func sup(r rune) (rune, error) {
+	s, ok := superscripts[r]
+	if !ok {
+		return r, fmt.Errorf("no corresponding superscript: %c", r)
+	}
+	return s, nil
+}
+
+// ToSuperscript converts a string to superscript to the utmost. It will use original
+// rune if there has no corresponding superscript for a letter.
+func ToSuperscript(s string) string {
+	buf := bytes.NewBuffer(make([]byte, 0, len(s)*3))
+	for _, r := range s {
+		sup, _ := sup(r)
+		buf.WriteRune(sup)
+	}
+	return buf.String()
+}
+
+// sub converts a rune to subscript. It returns the subscript or the original
+// rune and a error if there is no corresponding subscript.
+func sub(r rune) (rune, error) {
+	s, ok := subscripts[r]
+	if !ok {
+		return r, fmt.Errorf("no corresponding subscript: %c", r)
+	}
+	return s, nil
+}
+
+// ToSubscript converts a string to subscript to the utmost. It will use original
+// rune if there has no corresponding subscript for a letter.
+func ToSubscript(s string) string {
+	buf := bytes.NewBuffer(make([]byte, 0, len(s)*3))
+	for _, r := range s {
+		sub, _ := sub(r)
+		buf.WriteRune(sub)
+	}
+	return buf.String()
+}