Have a personal or library account? Click to login
Volatility Implications for Asset Returns Correlation Cover

Volatility Implications for Asset Returns Correlation

By:
Open Access
|Nov 2024

Figures & Tables

Figure 1.

VIX – volatility index, 1990–2024
VIX – volatility index, 1990–2024

Figure 2.

Distribution of correlation intervals by asset return periods
Distribution of correlation intervals by asset return periods

Figure 3.

Different responses to crisis of the range of holding/correlation periods of the price of silver and the broad US stock index during the period of the global financial crisis, 2007–2012
Different responses to crisis of the range of holding/correlation periods of the price of silver and the broad US stock index during the period of the global financial crisis, 2007–2012

Figure 4.

Average correlation of the rolling annual return of individual pairs of assets with a volatility index greater than 20 and less than 20
Average correlation of the rolling annual return of individual pairs of assets with a volatility index greater than 20 and less than 20

Rule of thumb for interpreting the size of a correlation coefficient

Size of correlationInterpretation
.90 to 1.00 (−.90 to −1.00)Very high positive (negative) correlation
.70 to .90 (−.70 to −.90)High positive (negative) correlation
.50 to .70 (−.50 to −.70)Moderate positive (negative) correlation
.30 to .50 (−.30 to −.50)Low positive (negative) correlation
.00 to .30 (.00 to −.30)Negligible correlation

Selected asset classes and data series and source description

Broad asset classesSelected asset classRepresentative ticker(s) or indexSample period and frequency
U.S. equitiesU.S. broad equityIndex: Wilshire 5000 Total Market Index, Close; Data series: WILL5000PR – FRED1970-12-31 to 1979-11-30 – monthly, 1979-12-03 to 2024-03-28 – daily
U.S. Large cap (S&P 500 index)Ticker: SPY - SPDR S&P 500 ETF Trust, Close; Data series: SPY – Yahoo Finance1980-01-02 to 2024-05-10 – daily
U.S. sectoral equitiesTickers: XLE, XLU, XLK, XLB, XLP, XLY, XLI, XLV, XLF - Select Sectors SPDR Funds, all Close; Data series: all – Yahoo Finance; IYR - iShares U.S. Real Estate ETF, all Close; Data series: all – Yahoo Finance Index: S&P Communication Services Select Sector Index, Close; Data series: ^SP500-50 – Yahoo FinanceXLE, XLU, XLK, XLB, XLP, XLY, XLI, XLV, XLF - 1998-12-22 to 2024-04-05 – daily; IYR - 2000-06-19 to 2024-04-05 – daily; ^SP500-50 - 1993-05-04 to 2024-04-05 – daily.
U.S. growth equitiesTicker: IUSG - iShares Core S&P U.S. Growth ETF, Close; Data series: IUSG - Yahoo Finance2000-07-28 to 2024-04-08 – daily
U.S. value equitiesTicker: IUSV - iShares Core S&P U.S. Value ETF, Close; Data series: IUSV – Yahoo Finance2000-08-04 to 2024-04-05 – daily
International equitiesDeveloped countries’ equities ex.-U.S.Ticker: VEA - Vanguard FTSE Developed Markets Index Fund ETF Shares, Close; Data series: VEA – Yahoo Finance2007-07-26 to 2024-04-05 – daily
EU equitiesTicker: EZU - iShares MSCI Eurozone ETF, Close; Data series: EZU – Yahoo Finance2000-07-31 to 2024-04-05 – daily
Japan equitiesTicker: EWJ - iShares MSCI Japan ETF, Close; Data Series: EWJ – Yahoo Finance1996-03-18 to 2024-04-05 – daily
Developing countries’ equities ex.-ChinaTicker: EMXC - iShares MSCI Emerging Markets ex China ETF, Close; Data Series: EMXC – Yahoo Finance2017-07-26 to 2024-04-05 – daily
Metals such as gold, silver, platinum and copperGoldIndex: LBMA Gold Price PM ($/ozt); Data Series: Global Gold price - Historical Data (1979-Present) – Kaggle1985-01-01 to 2023-10-06 - daily
SilverIndex: LBMA Silver Price ($/ozt); Data Series: Daily Silver prices (1968 – 2022) – Kaggle1968-01-02 to 2022-04-21 - daily
PlatinumIndex: Platinum London PM Fix ($/ozt); Data Series: Daily London Fix Prices 1990 – 2024 – Kaggle1990-04-02 to 2023-10-09 – daily
CopperIndex: FRED Global price of Copper ($/ton); Data Series: PCOPPUSDM – FRED1991-01-01 to 2024-02-01 – monthly
Oil, Energy, and Agriculture commodities – exposureOilTicker: DBO - Invesco DB Oil Fund, Close; Data Series: DBO – Yahoo Finance2007-01-05 to 2024-04-05 – daily
UraniumTicker: URA - Global X Uranium ETF, Close; Data Series: URA – Yahoo Finance2010-11-05 to 2024-04-05 – daily
Agriculture commoditiesTicker: DBA - Invesco DB Agriculture Fund, Close; Data Series: DBA – Yahoo Finance2007-01-05 to 2024-04-05 – daily
Alternative investment – exposureCryptocurrency – BitcoinTicker: GBTC - Grayscale Bitcoin Trust ETF (BTC), Close; Data Series: GBTC – Yahoo Finance2015-05-11 to 2024-04-08 – daily
Government bonds – exposureU.S. Long-term bondsTicker: TLT - iShares 20+ Year Treasury Bond ETF), Close; Data Series: TLT – Yahoo Finance2002-07-30 to 2024-04-19 – daily
U.S. Mid-term bondsTicker: IEF - iShares 7–10 Year Treasury Bond ETF, Close; Data Series: IEF – Yahoo Finance2002-07-30 to 2024-04-19 – daily
U.S. Inflation-linked bondsTicker: TIP - iShares TIPS Bond ETF, Close; Data Series: TIP – Yahoo Finance2003-12-05 to 2024-04-19 – daily
Developing countries’ government bondsTicker: EMB - iShares J.P. Morgan USD Emerging Markets Bond ETF, Close; Data Series: EMB – Yahoo Finance2007-12-19 to 2024-04-19 – daily
Corporate bonds - exposureU.S. Corporate bondsTicker: VCIT - Vanguard Intermediate-Term Corporate Bond Index Fund ETF Shares, Close; Data Series: VCIT – Yahoo Finance2009-11-23 to 2024-04-19 – daily
International corporate bondsTicker: CEMB - iShares J.P. Morgan EM Corporate Bond ETF, Close; Data Series: CEMB – Yahoo Finance2012-04-19 to 2024-04-19 – daily
Mixed bonds – exposureT-Bills, Corporate, MBS and Agency BondsTicker: BND - Vanguard Total Bond Market Index Fund, Close; Data Series: BND – Yahoo Finance2007-04-10 to 2024-04-19 – daily
Broad-based short-term investment gradeTicker: BSV - Vanguard Short-Term Bond Index Fund ETF Shares, Close; Data Series: BSV – Yahoo Finance2007-04-10 to 2024-04-19 – daily

The number of transition pairs with a change in the sign of correlation and the strength of correlation for each rolling period

3-month6-month1 year2 years5 years
x=pos, y=pos341356364308242
x=pos, y=neg1115211767
x=neg, y=pos643339532
x=neg, y=neg5163438992
Share of asset pairs which do not change the sign of the correlation16%10%13%15%17%
x<0.3; x>−0.3; y>−0.3; y<0.3 – weak correlation during both periods238196126114140
x<0.3; x>−0.3; y<−0.3; y>0.3 – weak correlation during VIX<20, stronger correlation during VIX>2082901047542
x>0.3; x<−0.3; y>−0.3; y<0.3 – stronger correlation during VIX<20, weak correlation during VIX>201219314056
x>0.3; x<−0.3; y<−0.3; y>0.3 – stronger correlation during both periods135162206238165
Share of asset pairs which changed correlation both from weak to stronger and from stronger to weak20%23%29%25%24%

Summary statistics of asset yearly rolling returns

CountMeanStdMinMax
BND4,0360.0280.050−0.1680.180
BSV4,0340.0200.029−0.0770.135
CEMB2,7700.0260.070−0.1870.294
DBA4,0910.0020.185−0.4700.642
DBO4,0910.0270.363−0.6461.374
EMB3,8590.0460.102−0.2570.644
EMXC1,4330.0410.199−0.3190.875
EWJ6,8090.0360.204−0.4340.854
EZU5,7070.0620.227−0.5910.814
GBTC1,9901.8353.404−0.89133.085
gold9,8540.0590.150−0.2920.709
IEF5,2180.0330.066−0.1810.205
IUSG5,7090.0920.192−0.5130.825
IUSV5,7030.0900.167−0.5080.797
IYR5,7360.1010.211−0.5921.250
PCOPPUSDM8,3730.0810.312−0.5811.486
platinum8,1470.0470.219−0.5430.978
silver10,4380.0450.303−0.7001.712
SPY10,9320.1030.163−0.4860.750
TIP4,8770.0340.057−0.1340.206
TLT5,2180.0450.130−0.3580.434
URA3,122−0.0350.381−0.6001.776
VCIT3,3730.0370.062−0.1820.211
VEA3,9510.0490.191−0.5250.787
WILL5000PR11,2820.1010.168−0.4880.817
XLB6,1110.0930.191−0.5451.017
XLE6,1110.1080.264−0.5951.166
XLF6,1110.0730.235−0.7211.507
XLI6,1110.0950.191−0.5550.995
XLK6,1110.1110.253−0.6380.878
XLP6,1110.0740.112−0.2990.452
XLU6,1110.0810.153−0.4630.504
XLV6,1110.0900.129−0.3370.557
XLY6,1110.1060.193−0.4951.003
^SP500-507,5320.0520.228−0.580.755

Average absolute difference of average correlation during VIX>20 and VIX<20 per different periods

Asset class pair3-month6-month1-year2-year5-year
International equities-Alternative investment0.3010.2690.1250.160n/a
International equities-Government bonds0.1400.1090.1680.2020.125
International equities-Mixed bonds0.2430.0580.1470.2470.066
International equities-Corporate bonds0.2680.1550.2650.2130.096
International equities-Metals such as gold, silver, platinum and copper0.1190.0940.2200.1670.105
U.S. equities-International equities0.1120.1500.1230.1200.078
U.S. equities-Oil. Energy. and Agriculture commodities0.1570.1370.2150.1120.181
U.S. equities-Alternative investment0.2290.1860.2290.165n/a
U.S. equities-Government bonds0.1430.1530.2160.1690.195
U.S. equities-Mixed bonds0.1730.1190.1440.2030.138
U.S. equities-Corporate bonds0.2030.1980.2180.1690.075
U.S. equities-Metals such as gold, silver, platinum and copper0.0710.1110.1770.2030.323
Oil, Energy, and Agriculture commodities - International equities0.1100.1370.2070.1180.103
Oil, Energy, and Agriculture commodities - Alternative investment0.2570.350.2240.374n/a
Oil, Energy, and Agriculture commodities - Government bonds0.1490.0860.1230.1230.110
Oil, Energy, and Agriculture commodities - Mixed bonds0.1350.040.1300.0870.164
Oil, Energy, and Agriculture commodities - Corporate bonds0.1670.0590.1290.1930.168
Oil, Energy, and Agriculture commodities - Metals such as gold, silver, platinum and copper0.1290.1460.1220.1640.057
Alternative investment - Government bonds0.1810.2270.1490.227n/a
Alternative investment - Mixed bonds0.0420.2720.0620.353n/a
Alternative investment - Corporate bonds0.1580.0870.1670.168n/a
Alternative investment - Metals such as gold, silver, platinum and copper0.1830.1800.2340.174n/a
Government bonds-Mixed bonds0.0720.0580.1280.1250.034
Government bonds-Corporate bonds0.0840.0660.1130.1190.043
Government bonds-Metals such as gold, silver, platinum and copper0.0950.1160.160.0930.261
Mixed bonds-Corporate bonds0.0840.0510.0720.1540.030
Mixed bonds-Metals such as gold, silver, platinum and copper0.0840.0670.0950.1730.050
Corporate bonds-Metals such as gold, silver, platinum and copper0.1700.0850.1060.0900.187
The absolute value of the correlation difference at VIX >20 and at VIX <= 20, the average value of the difference across all asset pairs0.1390.1320.1730.1600.160

Regression results for 1-year rolling correlation of 1-year rolling returns, asset pairs with difference >0_30 of average correlation between different volatility regimes

No.Ticker PairR^2Intcpt.SlopeP-valueStand. Err.Avg Corr VIX <=20Avg Corr VIX > 20Avg Corr VIX > 30Abs. difference at VIX > 20 and VIX <=20T-val.Conf Int LowerConf Int UpperShapiro-Wilk StatShapiro-Wilk P-valueBreusch-Pagan StatBreusch-Pagan P-valueDurbin-Watson Stat
1TLT-XLU0.260.81−0.030.000.0010.42−0.19−0.320.61−41.56−0.032−0.0290.9600.0003640.0000.0158
2IEF-XLU0.250.79−0.030.000.0010.41−0.16−0.330.57−40.35−0.031−0.0280.9610.0001890.0000.0150
3DBO-XLU0.20−0.310.020.000.0010.000.510.590.5231.460.0230.0270.9530.000150.0000.0124
4CEMB-XLY0.22−0.290.030.000.0010.150.650.720.5026.740.0300.0350.9660.000410.0000.0185
5EMB-XLY0.22−0.230.030.000.0010.150.630.730.4832.360.0260.0300.9620.000780.0000.0146
6GBTC-^SP500-500.25−0.100.030.000.0010.280.750.780.4824.520.0260.0310.8990.000360.0000.0209
7IEF-IYR0.150.69−0.030.000.0010.33−0.14−0.390.47−29.62−0.028−0.0250.9230.00050.0270.0082
8IYR-TLT0.150.66−0.030.000.0010.30−0.16−0.380.46−29.76−0.028−0.0250.9420.000390.0000.0083
9VEA-^SP500-500.19−0.050.020.000.0010.270.720.840.4629.730.0230.0260.9420.0001490.0000.0112
10CEMB-EWJ0.15−0.020.030.000.0010.320.770.800.4521.540.0240.0280.9270.00020.2010.0121
11DBO-XLP0.21−0.210.020.000.0010.100.550.650.4532.370.0230.0260.9610.000190.0000.0130
12GBTC-URA0.27−0.240.030.000.0010.140.580.730.4425.620.0260.0310.9800.000460.0000.0232
13BSV-XLU0.100.57−0.020.000.0010.430.000.040.43−21.10−0.017−0.0140.9760.0007090.0000.0058
14VCIT-XLU0.160.82−0.020.000.0010.510.090.140.42−24.45−0.025−0.0210.9630.0009760.0000.0129
15PCOPPUSDM-XLV0.23−0.220.030.000.0010.120.540.660.4242.070.0250.0270.9550.0001760.0000.0136
16GBTC-silver0.14−0.030.020.000.0010.160.570.610.4114.610.0140.0190.9110.00040.0480.0104
17PCOPPUSDM-WILL5000PR0.18−0.260.030.000.0010.140.550.700.4141.070.0270.0300.9300.0002320.0000.0092
18GBTC-PCOPPUSDM0.180.010.020.000.0010.300.700.760.4019.530.0210.0250.9190.000310.0000.0139
19BND-XLU0.070.58−0.010.000.0010.500.100.220.40−16.83−0.013−0.0110.9710.0008520.0000.0039
20CEMB-EZU0.100.100.020.000.0010.380.780.860.4017.270.0200.0250.9120.0001260.0000.0079
21GBTC-XLY0.280.080.020.000.0010.370.750.790.3926.360.0210.0240.9170.000440.0000.0245
22DBA-XLV0.20−0.230.020.000.0010.040.430.530.3830.870.0190.0220.9820.000390.0000.0119
23CEMB-IUSG0.160.050.020.000.0010.360.740.770.3821.920.0210.0250.8990.000100.0020.0125
24DBA-XLP0.18−0.190.020.000.0010.090.470.580.3829.480.0200.0230.9660.000140.0000.0109
25URA-^SP500-500.22−0.060.030.000.0010.290.670.770.3828.820.0240.0270.9620.00080.0040.0190
26EMB-EWJ0.10−0.010.020.000.0010.240.610.640.3820.570.0170.0210.9310.000650.0000.0061
27BND-IYR0.070.68−0.010.000.0010.540.170.150.37−16.58−0.016−0.0120.9130.0003610.0000.0037
28BSV-IYR0.100.65−0.020.000.0010.490.120.000.37−20.49−0.017−0.0140.9460.0004790.0000.0055
29IUSG-PCOPPUSDM0.18−0.040.020.000.0010.280.650.750.3734.900.0220.0240.9120.0001400.0000.0100
30IYR-URA0.180.080.020.000.0010.360.720.790.3625.310.0200.0230.9480.00000.8920.0144
31VCIT-XLY0.08−0.220.020.000.0010.040.400.300.3616.520.0170.0220.9620.00000.5210.0061
32EZU-PCOPPUSDM0.160.080.020.000.0010.350.710.800.3631.800.0190.0220.9090.0001540.0000.0084
33DBO-IYR0.14−0.090.020.000.0010.180.540.630.3625.490.0190.0220.9300.000350.0000.0083
34EZU-^SP500-500.130.000.020.000.0010.290.650.770.3629.130.0200.0230.9370.0002510.0000.0069
35TLT-XLE0.120.04−0.020.000.001−0.19−0.55−0.650.36−26.26−0.019−0.0160.9560.00010.2990.0065
36DBA-EWJ0.13−0.230.020.000.0010.060.420.550.3624.490.0200.0230.9300.0001100.0000.0075
37PCOPPUSDM-XLY0.17−0.250.030.000.0010.120.470.670.3535.230.0240.0270.9380.000330.0000.0096
38EWJ-TIP0.09−0.400.020.000.001−0.160.200.250.3521.030.0170.0210.9370.000670.0000.0045
39silver-XLV0.20−0.400.020.000.001−0.100.260.410.3536.310.0210.0230.9670.000430.0000.0107
40DBA-XLY0.16−0.270.020.000.0010.040.400.530.3527.120.0200.0240.9490.000470.0000.0092
41PCOPPUSDM-SPY0.15−0.200.030.000.0010.170.520.660.3537.520.0240.0270.9220.0001680.0000.0077
42CEMB-VEA0.110.220.020.000.0010.470.820.860.3517.800.0170.0220.8880.000970.0000.0084
43EWJ-URA0.19−0.130.030.000.0010.250.590.730.3526.140.0250.0290.9500.00040.0470.0157
44EMB-EZU0.090.090.020.000.0010.320.670.700.3519.360.0160.0200.9140.0001220.0000.0054
45TLT-XLP0.120.35−0.020.000.0010.05−0.29−0.450.35−26.44−0.023−0.0200.9260.00090.0030.0065
46EZU-silver0.17−0.070.020.000.0010.190.530.610.3431.460.0180.0200.9490.000380.0000.0088
47DBA-VCIT0.100.62−0.020.000.0010.340.00−0.270.34−18.95−0.023−0.0180.9380.000570.0000.0081
48EWJ-IYR0.17−0.100.020.000.0010.190.530.620.3433.590.0200.0220.9550.00080.0040.0091
49silver-VEA0.20−0.030.020.000.0010.210.550.690.3428.220.0170.0190.9520.0001460.0000.0114
50EMB-IUSG0.130.060.020.000.0010.310.650.700.3423.000.0170.0200.9080.000540.0000.0075
51TIP-XLY0.09−0.330.020.000.001−0.100.240.320.3421.670.0170.0200.9640.000650.0000.0048
52silver-TLT0.110.32−0.020.000.0010.06−0.28−0.520.33−23.31−0.021−0.0180.9710.0001950.0000.0055
53IEF-XLP0.130.39−0.020.000.0010.09−0.24−0.440.33−26.77−0.023−0.0200.9480.000180.0000.0067
54IUSG-silver0.15−0.180.020.000.0010.080.410.500.3329.900.0180.0210.9710.00020.1690.0078
55DBA-TLT0.100.23−0.020.000.001−0.01−0.34−0.530.33−20.89−0.020−0.0170.9670.00000.7840.0056
56DBA-IUSG0.17−0.070.020.000.0010.190.520.620.3328.490.0180.0200.9570.00010.3510.0102
57TLT-XLV0.120.25−0.020.000.001−0.04−0.36−0.490.33−26.59−0.022−0.0190.9290.000390.0000.0067
58URA-XLY0.18−0.030.030.000.0010.340.670.780.3225.420.0240.0280.9230.000220.0000.0149
59GBTC-WILL5000PR0.230.180.020.000.0010.430.750.800.3223.250.0180.0210.8900.00050.0210.0189
60platinum-XLV0.15−0.220.020.000.0010.070.390.460.3232.130.0190.0220.9510.0002720.0000.0082
61EMB-XLF0.120.040.020.000.0010.300.620.700.3222.750.0170.0210.9440.0002340.0000.0075
62IUSV-PCOPPUSDM0.140.040.020.000.0010.320.630.720.3130.190.0190.0210.9060.000180.0000.0077
63IYR-VCIT0.140.94−0.020.000.0010.730.420.370.31−22.93−0.018−0.0150.8970.0002890.0000.0114
64GBTC-IUSV0.170.060.020.000.0010.340.650.710.3119.180.0190.0230.8620.000460.0000.0128
65TLT-^SP500-500.090.40−0.020.000.0010.11−0.19−0.460.31−22.15−0.022−0.0180.9600.000140.0000.0047
66EWJ-XLU0.13−0.400.020.000.001−0.090.220.410.3029.870.0200.0230.9780.0001920.0000.0069
67EMB-XLI0.080.180.020.000.0010.390.690.730.3018.230.0140.0180.8820.0001960.0000.0048
68CEMB-WILL5000PR0.110.240.020.000.0010.470.780.810.3018.150.0160.0200.8890.000460.0000.0087
69EMB-VEA0.080.200.020.000.0010.400.700.720.3018.210.0140.0170.9050.000790.0000.0049
70EMB-XLV0.14−0.050.020.000.0010.210.510.670.3024.530.0170.0200.9620.0001980.0000.0086
71EZU-TIP0.08−0.280.020.000.001−0.070.230.310.3019.540.0150.0180.9580.000600.0000.0040
72IUSG-TIP0.06−0.190.020.000.0010.000.300.330.3017.900.0140.0170.9530.000970.0000.0034
73DBA-SPY0.140.030.020.000.0010.260.560.630.3024.940.0160.0180.9280.000310.0000.0080
74IYR-PCOPPUSDM0.16−0.140.020.000.0010.180.470.640.3032.040.0200.0230.9550.00040.0580.0085
75CEMB-XLI0.090.280.020.000.0010.500.800.840.3016.330.0150.0190.8450.000640.0000.0071
76URA-XLF0.190.120.020.000.0010.430.720.820.3026.020.0200.0240.9360.00030.0700.0156

1-year rolling volatility implications on annual rolling asset returns correlation, sample table of regression results_

Ticker PairTLT-XLUIEF-XLUDBO-XLUCEMB-XLYEMB-XLYGBTC-^SP500-50IEF-IYRIYR-TLTVEA-^SP500-50
R^20.260.250.200.220.220.250.150.150.19
Intercept0.810.79−0.31−0.29−0.23−0.100.690.66−0.05
Slope−0.03−0.030.020.030.030.03−0.03−0.030.02
P-value0.000.000.000.000.000.000.000.000.00
Standard Error0.0010.0010.0010.0010.0010.0010.0010.0010.001
Avg Corr VIX <= 200.420.410.000.150.150.280.330.300.27
Avg Corr VIX > 20−0.19−0.160.510.650.630.75−0.14−0.160.72
Avg Corr VIX > 30−0.32−0.330.590.720.730.78−0.39−0.380.84
Absolute difference at VIX > 20 and VIX <= 200.610.570.520.500.480.480.470.460.46
T-value−41.56−40.3531.4626.7432.3624.52−29.62−29.7629.73
Conf Int Lower−0.032−0.0310.0230.0300.0260.026−0.028−0.0280.023
Conf Int Upper−0.029−0.0280.0270.0350.0300.031−0.025−0.0250.026
Shapiro-Wilk Stat0.9600.9610.9530.9660.9620.8990.9230.9420.942
Shapiro-Wilk P-value0.0000.0000.0000.0000.0000.0000.0000.0000.000
Breusch-Pagan Stat36418915417836539149
Breusch-Pagan P-value0.0000.0000.0000.0000.0000.0000.0270.0000.000
Durbin-Watson Stat0.01580.01500.01240.01850.01460.02090.00820.00830.0112
DOI: https://doi.org/10.2478/ceej-2024-0027 | Journal eISSN: 2543-6821 | Journal ISSN: 2544-9001
Language: English
Page range: 424 - 446
Published on: Nov 23, 2024
Published by: Sciendo
In partnership with: Paradigm Publishing Services
Publication frequency: 1 times per year

© 2024 Illia Ivanov, published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 License.