Allow single-letter prefix in page number

data/source.csv

@@ -95,7 +95,7 @@ keck2001,Lothar Keck,2001,thesis,Climate significance of stable isotope records
 khalzan2022,Purevdagva Khalzan | Akiko Sakai | Koji Fujita,2022,article-journal,"Mass balance of four Mongolian glaciers: in-situ measurements, long-term reconstruction and sensitivity analysis",https://doi.org/10.3389/feart.2021.785306,en,Frontiers in Earth Science,9,,785306,,,,,
 khmelevskoy1963,И. Ф. Хмелевской [I. F. Khmelevskoy],1963,book,"Температура снега, фирна и льда: Стационарные наблюдения на станции Барьер Сомнений и маршрутные исследования [Temperature of snow, firn and ice: Stationary observations at the station Barier Somneiy and en route researches]",,ru,,2,,,,,Материалы Гляциологических Исследований: Новая Земля [Data of Glaciological Studies: Novaya Zemlya],,Акаде́мия нау́к СССР > Институт Географии [Academy of Sciences of the USSR > Institute of Geography]
 khmelevskoy1964,И. Ф. Хмелевской [I. F. Khmelevskoy],1964,book,"Температура снега, фирна и льда: Стационарные наблюдения на станции Ледораздельная [Temperature of snow, firn and ice: Stationary observations at the station Ledorazdelnaya]",,ru,,1,,,,,Материалы Гляциологических Исследований: Новая Земля [Data of Glaciological Studies: Novaya Zemlya],,Акаде́мия нау́к СССР > Институт Географии [Academy of Sciences of the USSR > Institute of Geography]
-khromova2022,T. E. Khromova | G. A. Nosenko | A. F. Glazovsky | A. Ya. Muraviev | S. A. Nikitin | I. I. Lavrentiev,2022,article-journal,New inventory of Russian glaciers based on satellite data (2016–2019),https://doi.org/10.1134/S0097807822070065,en,Water Resources,49,,S55-S68,,,,,Springer Nature
+khromova2022,T. E. Khromova | G. A. Nosenko | A. F. Glazovsky | A. Ya. Muraviev | S. A. Nikitin | I. I. Lavrentiev,2022,article-journal,New inventory of Russian glaciers based on satellite data (2016–2019),https://doi.org/10.1134/S0097807822070065,en,Water Resources,49,1,S55-S68,,,,,Pleiades Publishing
 kinnard2006,Christophe Kinnard | Christian M. Zdanowicz | David A. Fisher | Cameron P. Wake,2006,article-journal,Calibration of an ice-core glaciochemical (sea-salt) record with sea-ice variability in the Canadian Arctic,https://doi.org/10.3189/172756406781811349,en,Annals of Glaciology,44,,383-390,,,,,
 kinnard2020,Christophe Kinnard | Patrick Ginot | Arzhan Surazakov | Shelley MacDonell | Lindsey Nicholson | Nicolas Patris | Antoine Rabatel | Andres Rivera | Francisco A. Squeo,2020,article-journal,"Mass balance and climate history of a high-altitude glacier, desert Andes of Chile",https://doi.org/10.3389/feart.2020.00040,en,Frontiers in Earth Science,8,,,,,,,
 koerner1968,R. M. Koerner,1968,article-journal,"Fabric analysis of a core from the Meighen Ice Cap, Northwest Territories, Canada",https://doi.org/10.3189/S0022143000020621,en,Journal of Glaciology,7,51,421-430,,,,,

datapackage.yaml

@@ -181,10 +181,10 @@ resources:
           constraints:
             pattern: '[a-zA-Z]?[0-9]+(-[0-9]+)?'
         - name: page
-          description: Page number (e.g. 1) or range (e.g. 1-2) of the item in the container.
+          description: Page number (e.g. 1) or range (e.g. 1-2) of the item in the container, with an optional letter prefix (e.g. S1).
           type: string
           constraints:
-            pattern: '[0-9]+(-[0-9]+)?'
+            pattern: '[a-zA-Z]?[0-9]+(-[a-zA-Z]?[0-9]+)?'
         - name: version
           description: Version number (e.g. 1.0) of the item.
           type: string