diff --git a/Classes/PHPExcel/Calculation/Engineering.php b/Classes/PHPExcel/Calculation/Engineering.php
index efae2e24..38782f8f 100644
--- a/Classes/PHPExcel/Calculation/Engineering.php
+++ b/Classes/PHPExcel/Calculation/Engineering.php
@@ -771,24 +771,25 @@ class PHPExcel_Calculation_Engineering {
 
 
 	/**
-	 * BESSELI
+	 *	BESSELI
 	 *
-	 * Returns the modified Bessel function, which is equivalent to the Bessel function evaluated for
-	 * purely imaginary arguments
+	 *	Returns the modified Bessel function, which is equivalent to the Bessel function evaluated for
+	 *		purely imaginary arguments
 	 *
-	 * Excel Function:
+	 *	Excel Function:
 	 *		BESSELI(x,ord)
 	 *
-	 * @access	public
-	 * @category Engineering Functions
-	 * @param	float		$x		The value at which to evaluate the function.
+	 *	@access	public
+	 *	@category Engineering Functions
+	 *	@param	float		$x		The value at which to evaluate the function.
 	 *								If x is nonnumeric, BESSELI returns the #VALUE! error value.
-	 * @param	integer		$ord	The order of the Bessel function. If n is not an integer, it is truncated.
+	 *	@param	integer		$ord	The order of the Bessel function. If n is not an integer, it is truncated.
 	 *								If $ord is nonnumeric, BESSELI returns the #VALUE! error value.
 	 *								If $ord < 0, BESSELI returns the #NUM! error value.
-	 * @return	float
+	 *	@return	float
 	 *
-	 * @TODO Better handling of the approximation method to support the differences between Excel/Gnumeric and Open/Libre Office
+	 *	@TODO Better handling of the approximation method to support the differences between Excel/Gnumeric
+	 *		and Open/Libre Office
 	 *
 	 */
 	public static function BESSELI($x, $ord) {
@@ -2259,33 +2260,32 @@ class PHPExcel_Calculation_Engineering {
 
 
 	/**
-	 * ERF
+	 *	ERF
 	 *
-	 * Returns the error function integrated between lower_limit and upper_limit
+	 *	Returns the error function integrated between the lower and upper bound arguments.
 	 *
-	 * Excel Function:
+	 *	Note: In Excel 2007 or earlier, if you input a negative value for the upper or lower bound arguments,
+	 *			the function would return a #NUM! error. However, in Excel 2010, the function algorithm was
+	 *			improved, so that it can now calculate the function for both positive and negative ranges.
+	 *			PHPExcel follows Excel 2010 behaviour, and accepts nagative arguments.
+	 *
+	 *	Excel Function:
 	 *		ERF(lower[,upper])
 	 *
-	 * @param	float		$lower	lower bound for integrating ERF
-	 * @param	float		$upper	upper bound for integrating ERF.
+	 *	@param	float		$lower	lower bound for integrating ERF
+	 *	@param	float		$upper	upper bound for integrating ERF.
 	 *								If omitted, ERF integrates between zero and lower_limit
-	 * @return	int
+	 *	@return	float
 	 */
-	public static function ERF($lower, $upper = null) {
+	public static function ERF($lower, $upper = NULL) {
 		$lower	= PHPExcel_Calculation_Functions::flattenSingleValue($lower);
 		$upper	= PHPExcel_Calculation_Functions::flattenSingleValue($upper);
 
 		if (is_numeric($lower)) {
-			if ($lower < 0) {
-				return PHPExcel_Calculation_Functions::NaN();
-			}
 			if (is_null($upper)) {
 				return self::_erfVal($lower);
 			}
 			if (is_numeric($upper)) {
-				if ($upper < 0) {
-					return PHPExcel_Calculation_Functions::NaN();
-				}
 				return self::_erfVal($upper) - self::_erfVal($lower);
 			}
 		}
@@ -2326,23 +2326,25 @@ class PHPExcel_Calculation_Engineering {
 
 
 	/**
-	 * ERFC
+	 *	ERFC
 	 *
-	 * Returns the complementary ERF function integrated between x and infinity
+	 *	Returns the complementary ERF function integrated between x and infinity
 	 *
-	 * Excel Function:
+	 *	Note: In Excel 2007 or earlier, if you input a negative value for the lower bound argument,
+	 *		the function would return a #NUM! error. However, in Excel 2010, the function algorithm was
+	 *		improved, so that it can now calculate the function for both positive and negative x values.
+	 *			PHPExcel follows Excel 2010 behaviour, and accepts nagative arguments.
+	 *
+	 *	Excel Function:
 	 *		ERF(x)
 	 *
-	 * @param	float		$x		The lower bound for integrating ERF
-	 * @return	int
+	 *	@param	float	$x	The lower bound for integrating ERF
+	 *	@return	float
 	 */
 	public static function ERFC($x) {
-		$x	= PHPExcel_Calculation_Functions::flattenSingleValue($x);
+		$x = PHPExcel_Calculation_Functions::flattenSingleValue($x);
 
 		if (is_numeric($x)) {
-			if ($x < 0) {
-				return PHPExcel_Calculation_Functions::NaN();
-			}
 			return self::_erfcVal($x);
 		}
 		return PHPExcel_Calculation_Functions::VALUE();
diff --git a/changelog.txt b/changelog.txt
index bdfa9644..c10a41c9 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -30,6 +30,7 @@ Fixed in develop branch:
                          tcPDF Library has now been removed from the deployment bundle
 - Feature:  (MBaker)     Initial version of HTML Reader
 - Feature:  (Progi1984) & (blazzy) Work items 9605 - Implement support for AutoFilter in PHPExcel_Writer_Excel5
+- Feature:  (MBaker)     Modified ERF and ERFC Engineering functions to accept Excel 2010's modified acceptance of negative arguments
 - Bugfix:   (cyberconte) Patch 12318 - OOCalc cells containing <text:span> inside the <text:p> tag
 - Bugfix:   (schir1964)  Fix to listWorksheetInfo() method for OOCalc Reader
 - Bugfix:   (MBaker)     Support for "e" (epoch) date format mask
diff --git a/unitTests/PHPExcel/Calculation/EngineeringTest.php b/unitTests/PHPExcel/Calculation/EngineeringTest.php
index 5e33769a..030ccb53 100644
--- a/unitTests/PHPExcel/Calculation/EngineeringTest.php
+++ b/unitTests/PHPExcel/Calculation/EngineeringTest.php
@@ -405,7 +405,7 @@ class EngineeringTest extends PHPUnit_Framework_TestCase
 		$args = func_get_args();
 		$expectedResult = array_pop($args);
 		$result = call_user_func_array(array('PHPExcel_Calculation_Engineering','ERF'),$args);
-		$this->assertEquals($expectedResult, $result, NULL, 1E-6);
+		$this->assertEquals($expectedResult, $result, NULL, 1E-12);
 	}
 
     public function providerERF()
@@ -421,7 +421,7 @@ class EngineeringTest extends PHPUnit_Framework_TestCase
 		$args = func_get_args();
 		$expectedResult = array_pop($args);
 		$result = call_user_func_array(array('PHPExcel_Calculation_Engineering','ERFC'),$args);
-		$this->assertEquals($expectedResult, $result, NULL, 1E-6);
+		$this->assertEquals($expectedResult, $result, NULL, 1E-12);
 	}
 
     public function providerERFC()
diff --git a/unitTests/rawTestData/Calculation/Engineering/ERF.data b/unitTests/rawTestData/Calculation/Engineering/ERF.data
index f7888d5a..d52cf32c 100644
--- a/unitTests/rawTestData/Calculation/Engineering/ERF.data
+++ b/unitTests/rawTestData/Calculation/Engineering/ERF.data
@@ -1,121 +1,124 @@
-0,	0.0
-0.01,	0.0112834155558496
-0.05,	0.0563719777970166
-0.1,	0.1124629160182850
-0.125,	0.1403162048013340
-0.15,	0.1679959714273630
-0.2,	0.2227025892104780
-0.25,	0.2763263901682370
-0.3,	0.3286267594591270
-0.35,	0.3793820535623100
-0.4,	0.4283923550466680
-0.45,	0.4754817197869240
-0.5,	0.5204998778130470
-0.6,	0.6038560908479260
-0.7,	0.6778011938374180
-0.8,	0.7421009647076610
-0.9,	0.7969082124228320
-1,	0.8427007929497150
-1.1,	0.8802050695740820
-1.2,	0.9103139782296350
-1.3,	0.9340079449406520
-1.4,	0.9522851197626490
-1.5,	0.9661051464753110
-1.75,	0.9866716712191820
-2,	0.9953222650189530
-2.5,	0.9995930479825550
-3,	0.9999779095030010
-3.5,	0.9999992569016280
-4,	0.9999999845827420
-4.5,	0.9999999998033840
-5,	0.9999999999984630
-5.5,	0.9999999999999930
-6,	1.0
-32,	1.0
--0.1,	-0.1124629160182850
--1,	-0.8427007929497150
-TRUE,	"#VALUE!"
-FALSE,	"#VALUE!"
-2,	0.9953222650189530
-"TWO",	"#VALUE!"
--1.5,	-1.5,	0
--0.75,	-1.5,	-0.254949513
-0,	-1.5,	-0.966105146
-0.75,	-1.5,	-1.67726078
-1.5,	-1.5,	-1.932210293
-2.25,	-1.5,	-1.96464243
-3,	-1.5,	-1.966083056
-3.75,	-1.5,	-1.966105033
-4.5,	-1.5,	-1.966105146
--1.5,	-0.75,	0.254949513
--0.75,	-0.75,	0
-0,	-0.75,	-0.711155634
-0.75,	-0.75,	-1.422311267
-1.5,	-0.75,	-1.67726078
-2.25,	-0.75,	-1.709692917
-3,	-0.75,	-1.711133543
-3.75,	-0.75,	-1.71115552
-4.5,	-0.75,	-1.711155633
--1.5,	0,	0.966105146
--0.75,	0,	0.711155634
-0,	0,	0
-0.75,	0,	-0.711155634
-1.5,	0,	-0.966105146
-2.25,	0,	-0.998537283
-3,	0,	-0.99997791
-3.75,	0,	-0.999999886
-4.5,	0,	-1
--1.5,	0.75,	1.67726078
--0.75,	0.75,	1.422311267
-0,	0.75,	0.711155634
-0.75,	0.75,	0
-1.5,	0.75,	-0.254949513
-2.25,	0.75,	-0.28738165
-3,	0.75,	-0.288822276
-3.75,	0.75,	-0.288844253
-4.5,	0.75,	-0.288844366
--1.5,	1.5,	1.932210293
--0.75,	1.5,	1.67726078
-0,	1.5,	0.966105146
-0.75,	1.5,	0.254949513
-1.5,	1.5,	0
-2.25,	1.5,	-0.032432137
-3,	1.5,	-0.033872763
-3.75,	1.5,	-0.03389474
-4.5,	1.5,	-0.033894853
--1.5,	2.25,	1.96464243
--0.75,	2.25,	1.709692917
-0,	2.25,	0.998537283
-0.75,	2.25,	0.28738165
-1.5,	2.25,	0.032432137
-2.25,	2.25,	0
-3,	2.25,	-0.001440626
-3.75,	2.25,	-0.001462603
-4.5,	2.25,	-0.001462716
--1.5,	3,	1.966083056
--0.75,	3,	1.711133543
-0,	3,	0.99997791
-0.75,	3,	0.288822276
-1.5,	3,	0.033872763
-2.25,	3,	0.001440626
-3,	3,	0
-3.75,	3,	-2.19768E-05
-4.5,	3,	-2.20903E-05
--1.5,	3.75,	1.966105033
--0.75,	3.75,	1.71115552
-0,	3.75,	0.999999886
-0.75,	3.75,	0.288844253
-1.5,	3.75,	0.03389474
-2.25,	3.75,	0.001462603
-3,	3.75,	2.19768E-05
-3.75,	3.75,	0
-4.5,	3.75,	-1.13531E-07
--1.5,	4.5,	1.966105146
--0.75,	4.5,	1.711155633
-0,	4.5,	1
-0.75,	4.5,	0.288844366
-1.5,	4.5,	0.033894853
-2.25,	4.5,	0.001462716
-3,	4.5,	2.20903E-05
-3.75,	4.5,	1.13531E-07
-4.5,	4.5,	0
+# lower	bound	upper bound	Result
+0,				0.0
+0.01,				0.0112834155558496
+0.05,				0.0563719777970166
+0.1,				0.1124629160182850
+0.125,				0.1403162048013340
+0.15,				0.1679959714273630
+0.2,				0.2227025892104780
+0.25,				0.2763263901682370
+0.3,				0.3286267594591270
+0.35,				0.3793820535623100
+0.4,				0.4283923550466680
+0.45,				0.4754817197869240
+0.5,				0.5204998778130470
+0.6,				0.6038560908479260
+0.7,				0.6778011938374180
+0.8,				0.7421009647076610
+0.9,				0.7969082124228320
+1,				0.8427007929497150
+1.1,				0.8802050695740820
+1.2,				0.9103139782296350
+1.3,				0.9340079449406520
+1.4,				0.9522851197626490
+1.5,				0.9661051464753110
+1.75,				0.9866716712191820
+2,				0.9953222650189530
+2.5,				0.9995930479825550
+3,				0.9999779095030010
+3.5,				0.9999992569016280
+4,				0.9999999845827420
+4.5,				0.9999999998033840
+5,				0.9999999999984630
+5.5,				0.9999999999999930
+6,				1.0
+32,				1.0
+-0.1,				-0.1124629160182850
+-1,				-0.8427007929497150
+TRUE,				"#VALUE!"
+FALSE,				"#VALUE!"
+"2",				0.9953222650189530
+"TWO",				"#VALUE!"
+-1.5,		-1.5,		0.0
+-0.75,		-1.5,		-0.2549495128217960
+0,		-1.5,		-0.9661051464753110
+0.75,		-1.5,		-1.6772607801288300
+1.5,		-1.5,		-1.9322102929506200
+2.25,		-1.5,		-1.9646424298886300
+3,		-1.5,		-1.9660830559783100
+3.75,		-1.5,		-1.9661050327480500
+4.5,		-1.5,		-1.9661051462786900
+-1.5,		-0.75,		0.2549495128217960
+-0.75,		-0.75,		0.0
+0,		-0.75,		-0.7111556336535150
+0.75,		-0.75,		-1.4223112673070300
+1.5,		-0.75,		-1.6772607801288300
+2.25,		-0.75,		-1.7096929170668300
+3,		-0.75,		-1.7111335431565200
+3.75,		-0.75,		-1.7111555199262600
+4.5,		-0.75,		-1.7111556334569000
+-1.5,		0,		0.9661051464753110
+-0.75,		0,		0.7111556336535150
+0,		0,		0.0
+0.75,		0,		-0.7111556336535150
+1.5,		0,		-0.9661051464753110
+2.25,		0,		-0.9985372834133190
+3,		0,		-0.9999779095030010
+3.75,		0,		-0.9999998862727430
+4.5,		0,		-0.9999999998033840
+-1.5,		0.75,		1.6772607801288300
+-0.75,		0.75,		1.4223112673070300
+0,		0.75,		0.7111556336535150
+0.75,		0.75,		0.0
+1.5,		0.75,		-0.2549495128217960
+2.25,		0.75,		-0.2873816497598040
+3,		0.75,		-0.2888222758494860
+3.75,		0.75,		-0.2888442526192280
+4.5,		0.75,		-0.2888443661498690
+-1.5,		1.5,		1.9322102929506200
+-0.75,		1.5,		1.6772607801288300
+0,		1.5,		0.9661051464753110
+0.75,		1.5,		0.2549495128217960
+1.5,		1.5,		0.0
+2.25,		1.5,		-0.0324321369380081
+3,		1.5,		-0.0338727630276906
+3.75,		1.5,		-0.0338947397974326
+4.5,		1.5,		-0.0338948533280732
+-1.5,		2.25,		1.9646424298886300
+-0.75,		2.25,		1.7096929170668300
+0,		2.25,		0.9985372834133190
+0.75,		2.25,		0.2873816497598040
+1.5,		2.25,		0.0324321369380081
+2.25,		2.25,		0.0
+3,		2.25,		-0.0014406260896825
+3.75,		2.25,		-0.0014626028594246
+4.5,		2.25,		-0.0014627163900651
+-1.5,		3,		1.9660830559783100
+-0.75,		3,		1.7111335431565200
+0,		3,		0.9999779095030010
+0.75,		3,		0.2888222758494860
+1.5,		3,		0.0338727630276906
+2.25,		3,		0.0014406260896825
+3,		3,		0.0
+3.75,		3,		-0.0000219767697420
+4.5,		3,		-0.0000220903003826
+-1.5,		3.75,		1.9661050327480500
+-0.75,		3.75,		1.7111555199262600
+0,		3.75,		0.9999998862727430
+0.75,		3.75,		0.2888442526192280
+1.5,		3.75,		0.0338947397974326
+2.25,		3.75,		0.0014626028594246
+3,		3.75,		0.0000219767697420
+3.75,		3.75,		0.0
+4.5,		3.75,		-0.0000001135306406
+-1.5,		4.5,		1.9661051462786900
+-0.75,		4.5,		1.7111556334569000
+0,		4.5,		0.9999999998033840
+0.75,		4.5,		0.2888443661498690
+1.5,		4.5,		0.0338948533280732
+2.25,		4.5,		0.0014627163900651
+3,		4.5,		0.0000220903003826
+3.75,		4.5,		0.0000001135306406
+4.5,		4.5,		0.0
+5,		-1,		-1.8427007929481800
+-5,		1,		1.8427007929481800
diff --git a/unitTests/rawTestData/Calculation/Engineering/ERFC.data b/unitTests/rawTestData/Calculation/Engineering/ERFC.data
index d3c2fc57..3cdc3d5b 100644
--- a/unitTests/rawTestData/Calculation/Engineering/ERFC.data
+++ b/unitTests/rawTestData/Calculation/Engineering/ERFC.data
@@ -1,82 +1,41 @@
--2.5,	5,	0
--1.5,	-1.5,	0
--0.75,	-1.5,	0
-0,	-1.5,	0
-0.75,	-1.5,	0.288844366
-1.5,	-1.5,	0.033894854
-2.25,	-1.5,	0.001462717
-3,	-1.5,	2.20905E-05
-3.75,	-1.5,	1.13727E-07
-4.5,	-1.5,	1.96616E-10
--1.5,	-0.75,	0
--0.75,	-0.75,	0
-0,	-0.75,	0
-0.75,	-0.75,	0.288844366
-1.5,	-0.75,	0.033894854
-2.25,	-0.75,	0.001462717
-3,	-0.75,	2.20905E-05
-3.75,	-0.75,	1.13727E-07
-4.5,	-0.75,	1.96616E-10
--1.5,	0,	0
--0.75,	0,	0
-0,	0,	0
-0.75,	0,	0.288844366
-1.5,	0,	0.033894854
-2.25,	0,	0.001462717
-3,	0,	2.20905E-05
-3.75,	0,	1.13727E-07
-4.5,	0,	1.96616E-10
--1.5,	0.75,	0
--0.75,	0.75,	0
-0,	0.75,	0
-0.75,	0.75,	0.288844366
-1.5,	0.75,	0.033894854
-2.25,	0.75,	0.001462717
-3,	0.75,	2.20905E-05
-3.75,	0.75,	1.13727E-07
-4.5,	0.75,	1.96616E-10
--1.5,	1.5,	0
--0.75,	1.5,	0
-0,	1.5,	0
-0.75,	1.5,	0.288844366
-1.5,	1.5,	0.033894854
-2.25,	1.5,	0.001462717
-3,	1.5,	2.20905E-05
-3.75,	1.5,	1.13727E-07
-4.5,	1.5,	1.96616E-10
--1.5,	2.25,	0
--0.75,	2.25,	0
-0,	2.25,	0
-0.75,	2.25,	0.288844366
-1.5,	2.25,	0.033894854
-2.25,	2.25,	0.001462717
-3,	2.25,	2.20905E-05
-3.75,	2.25,	1.13727E-07
-4.5,	2.25,	1.96616E-10
--1.5,	3,	0
--0.75,	3,	0
-0,	3,	0
-0.75,	3,	0.288844366
-1.5,	3,	0.033894854
-2.25,	3,	0.001462717
-3,	3,	2.20905E-05
-3.75,	3,	1.13727E-07
-4.5,	3,	1.96616E-10
--1.5,	3.75,	0
--0.75,	3.75,	0
-0,	3.75,	0
-0.75,	3.75,	0.288844366
-1.5,	3.75,	0.033894854
-2.25,	3.75,	0.001462717
-3,	3.75,	2.20905E-05
-3.75,	3.75,	1.13727E-07
-4.5,	3.75,	1.96616E-10
--1.5,	4.5,	0
--0.75,	4.5,	0
-0,	4.5,	0
-0.75,	4.5,	0.288844366
-1.5,	4.5,	0.033894854
-2.25,	4.5,	0.001462717
-3,	4.5,	2.20905E-05
-3.75,	4.5,	1.13727E-07
-4.5,	4.5,	1.96616E-10
+# x value	Result
+0,		1.0
+0.01,		0.9887165844441500
+0.05,		0.9436280222029830
+0.1,		0.8875370839817150
+0.125,		0.8596837951986660
+0.15,		0.8320040285726360
+0.2,		0.7772974107895220
+0.25,		0.7236736098317630
+0.3,		0.6713732405408730
+0.35,		0.6206179464376900
+0.4,		0.5716076449533320
+0.45,		0.5245182802130760
+0.5,		0.4795001221869530
+0.6,		0.3961439091520740
+0.7,		0.3221988061625820
+0.8,		0.2578990352923390
+0.9,		0.2030917875771680
+1,		0.1572992070502850
+1.1,		0.1197949304259180
+1.2,		0.0896860217703646
+1.3,		0.0659920550593475
+1.4,		0.0477148802373512
+1.5,		0.0338948535246893
+1.75,		0.0133283287808176
+2,		0.0046777349810473
+2.5,		0.0004069520174450
+3,		0.0000220904969986
+3.5,		0.0000007430983723
+4,		0.0000000154172579
+4.5,		0.0000000001966160
+5,		0.0000000000015375
+5.5,		0.0000000000000074
+6,		0.0
+32,		0.0
+-0.1,		1.1124629160182900
+-1,		1.8427007929497100
+TRUE,		"#VALUE!"
+FALSE,		"#VALUE!"
+"2",		0.0046777349810473
+"TWO",		"#VALUE!"