| u | Unknown | | 60 | |
| i | Irregular | No fixed publication schedule | 60 | |
| e | Biennial | Once every two years | 60 | |
| a | Annual | Yearly | 60 | |
| b | Biannual | Twice a year, or once per academic semester | 60 | |
| t | Triannual | Three times a year, or once per academic term | 60 | |
| q | Quarterly | Four times a year | 60 | |
| s | Bimonthly | Six times per year | 60 | |
| m | Monthly | Once every month, or approximately twelve times per year | 60 | |
| f | Fortnightly | Once every two weeks, or approximately twenty five times per year | 60 | |
| w | Weekly | Or approximately fifty times per year | 60 | |
| d | Daily, or more frequently than weekly | At least twice a week | 60 | 66 |
| x | No future publications | Positive indication that the product is the last to be published in the collection, or that no further publications are planned | 60 | |