| Covers listed |
|
| 1967: | August, |
| 1974: | January, |
| 1975: | November, |
| 1978: | June, |
| 1979: | June, |
| 1986: | January, |
| 1987: | January, March, October, |
| 1988: | November, |
| 1989: | June, July, |
| 1991: | August, October, December, |
| 1992: | August, October, |
| 1995: | February, |
| 1996: | February, |
| 1997: | October, |
| 1998: | August, |
| 1999: | May, August, November, December, |
| 2000: | April, June, August, September, November, December, |
| 2001: | February, May, July, August, November, December, |
| 2002: | January, February, July, August, December, |
| 2003: | January, February, June, November, |
| 2004: | September, |
| 2005: | January, March, May, June, July, August, October, November, December, |
| 2006: | January, April, May, June, July, August, December, |
| 2007: | January, March, April, June, July, September, October, November, December, |
| 2008: | March, April, May, July, November, |
| 2009: | January, February, March, April, June, July, August, September, |
| 2010: | January, April, May, June, July, August, September, October, November, December, |
| 2011: | February, April, June, September, October, December, |
| 2012: | May, |
| 2013: | March, June, July, August, September, October, December, |
| 2014: | January, September, |
| 2015: | February, |
| 2016: | May, July, |
| 2017: | April, July, |
| 2018: | March, May, June, October, |
