diff --git a/notfound.go b/notfound.go
index 3950c35..dea9a59 100644
--- a/notfound.go
+++ b/notfound.go
@@ -2,6 +2,8 @@ package eol
 
 import (
 	"fmt"
+
+	"sourcecode.social/reiver/go-opt"
 )
 
 var _ error = internalNotFoundError{}
@@ -9,7 +11,15 @@ var _ error = internalNotFoundError{}
 type internalNotFoundError struct{
 	expected rune
 	actual rune
-	characterNumber uint64
+	circumstance internalCircumstance
+}
+
+func errNotFound(circumstance internalCircumstance, expected rune, actual rune) error {
+	return internalNotFoundError {
+		expected:expected,
+		actual:actual,
+		circumstance:circumstance,
+	}
 }
 
 func (receiver internalNotFoundError) Error() string {
@@ -21,23 +31,39 @@ func (receiver internalNotFoundError) Error() string {
 	var expected rune = receiver.expected
 	var actual   rune = receiver.actual
 
-	var characterNumber uint64 = receiver.characterNumber
+	var characterNumber uint64           = receiver.circumstance.CharacterNumber()
+	var eolSequence opt.Optional[string] = receiver.circumstance.EOLSequence()
 
 	switch expected {
 	case lf:
-		var s string =  fmt.Sprintf(`eol: line-feed (LF) character ('\n') (U+000A) not found for end-of-line character №%d — instead found %q (%U)`, characterNumber, actual, actual)
+		var s string = fmt.Sprintf(`eol: line-feed (LF) character ('\n') (U+000A) not found for end-of-line sequence character №%d — instead found %q (%U)`, characterNumber, actual, actual)
+		eolSequence.WhenSomething(func(sequence string){
+			s    = fmt.Sprintf(`eol: line-feed (LF) character ('\n') (U+000A) not found for end-of-line sequence %q character №%d — instead found %q (%U)`, sequence, characterNumber, actual, actual)
+		})
 		p = append(p, s...)
 	case cr:
-		var s string = fmt.Sprintf(`eol: carriage-return (CR) character ('\r') (U+000D) not found for end-of-line character №%d — instead found %q (%U)`, characterNumber, actual, actual)
+			var s string = fmt.Sprintf(`eol: carriage-return (CR) character ('\r') (U+000D) not found for end-of-line sequence character №%d — instead found %q (%U)`, characterNumber, actual, actual)
+		eolSequence.WhenSomething(func(sequence string){
+			s            = fmt.Sprintf(`eol: carriage-return (CR) character ('\r') (U+000D) not found for end-of-line sequence %q character №%d — instead found %q (%U)`, sequence, characterNumber, actual, actual)
+		})
 		p = append(p, s...)
 	case nel:
-		var s string = fmt.Sprintf(`eol: next-line (NEL) character (U+0085) not found for end-of-line character №%d — instead found %q (%U)`, characterNumber, actual, actual)
+		var s string = fmt.Sprintf(`eol: next-line (NEL) character (U+0085) not found for end-of-line sequence character №%d — instead found %q (%U)`, characterNumber, actual, actual)
+		eolSequence.WhenSomething(func(sequence string){
+			s    = fmt.Sprintf(`eol: next-line (NEL) character (U+0085) not found for end-of-line sequence %q character №%d — instead found %q (%U)`, sequence, characterNumber, actual, actual)
+		})
 		p = append(p, s...)
 	case ls:
-		var s string = fmt.Sprintf(`eol: line-separator (LS) character (U+2028) not found for end-of-line character №%d — instead found %q (%U)`, characterNumber, actual, actual)
+		var s string = fmt.Sprintf(`eol: line-separator (LS) character (U+2028) not found for end-of-line sequence character №%d — instead found %q (%U)`, characterNumber, actual, actual)
+		eolSequence.WhenSomething(func(sequence string){
+			s    = fmt.Sprintf(`eol: line-separator (LS) character (U+2028) not found for end-of-line sequence %q character №%d — instead found %q (%U)`, sequence, characterNumber, actual, actual)
+		})
 		p = append(p, s...)
 	default:
-		var s string = fmt.Sprintf(`eol: %q character (%U) not found for character №%d — instead found %q (%U)`, expected, expected, characterNumber, actual, actual)
+		var s string = fmt.Sprintf(`eol: %q character (%U) not found for sequence character №%d — instead found %q (%U)`, expected, expected, characterNumber, actual, actual)
+		eolSequence.WhenSomething(func(sequence string){
+			s    = fmt.Sprintf(`eol: %q character (%U) not found for sequence %q character №%d — instead found %q (%U)`, expected, expected, sequence, characterNumber, actual, actual)
+		})
 		p = append(p, s...)
 	}
 
diff --git a/problemreadingrune.go b/problemreadingrune.go
index aebf498..0dca87d 100644
--- a/problemreadingrune.go
+++ b/problemreadingrune.go
@@ -6,23 +6,29 @@ import (
 
 var _ error = internalProblemReadingRuneError{}
 
-func errProblemReadingRune(err error, runeNumber uint64) error {
+func errProblemReadingRune(circumstance internalCircumstance, err error) error {
 	return internalProblemReadingRuneError{
 		err:err,
-		runeNumber:runeNumber,
+		circumstance:circumstance,
 	}
 }
 
 type internalProblemReadingRuneError struct {
 	err error
-	runeNumber uint64
+	circumstance internalCircumstance
 }
 
 func (receiver internalProblemReadingRuneError) Error() string {
 	err := receiver.err
-	runeNumber := receiver.runeNumber
+	characterNumber := receiver.circumstance.CharacterNumber()
+	eolSequence := receiver.circumstance.EOLSequence()
 
-	return fmt.Sprintf("eol: problem reading character №%d of end-of-line sequence: %s", runeNumber, err)
+	var s string = fmt.Sprintf("eol: problem reading character №%d of end-of-line sequence: %s", characterNumber, err)
+	eolSequence.WhenSomething(func(sequence string){
+		s    = fmt.Sprintf("eol: problem reading character №%d of end-of-line sequence %q: %s", characterNumber, sequence, err)
+	})
+
+	return s
 }
 
 func (receiver internalProblemReadingRuneError) Unwrap() error {
diff --git a/problemunreadingrune.go b/problemunreadingrune.go
index 12a2354..e049934 100644
--- a/problemunreadingrune.go
+++ b/problemunreadingrune.go
@@ -6,26 +6,32 @@ import (
 
 var _ error = internalProblemUnreadingRuneError{}
 
-func errProblemUnreadingRune(err error, runeNumber uint64, r rune) error {
+func errProblemUnreadingRune(circumstance internalCircumstance, err error, r rune) error {
 	return internalProblemUnreadingRuneError{
 		err:err,
-		runeNumber:runeNumber,
 		r:r,
+		circumstance:circumstance,
 	}
 }
 
 type internalProblemUnreadingRuneError struct {
 	err error
-	runeNumber uint64
 	r rune
+	circumstance internalCircumstance
 }
 
 func (receiver internalProblemUnreadingRuneError) Error() string {
 	err := receiver.err
-	runeNumber := receiver.runeNumber
 	r := receiver.r
+	characterNumber := receiver.circumstance.CharacterNumber()
+	eolSequence := receiver.circumstance.EOLSequence()
 
-	return fmt.Sprintf("eol: problem unreading character №%d (%q (%U)) of end-of-line sequence: %s", runeNumber, r, r, err)
+	var s string = fmt.Sprintf("eol: problem unreading character №%d (%q (%U)) of end-of-line sequence: %s", characterNumber, r, r, err)
+	eolSequence.WhenSomething(func(sequence string){
+		s    = fmt.Sprintf("eol: problem unreading character №%d (%q (%U)) of end-of-line sequence %q: %s", characterNumber, r, r, sequence, err)
+	})
+
+	return s
 }
 
 func (receiver internalProblemUnreadingRuneError) Unwrap() error {