4 June – Saint Quirinus of Sescia

Annus Dierus Sanctorum
Expedit ei, ut Suspendatur mola in Collo eius, et demergatus in profundum.
It were better for him that a stone should be hanged about his neck, and that he should be drowned in the depth.
  Matthew 18.6

Modern Hagiography

Bibliotheca Sanctorum

Martyrologium Romanum

Roman Martyrology

Sanctorale Catholicum

Lives of the Saints by Alban Butler.

Lives of the Saints by Sabine Baring-Gould.

Our Birthday Bouquet Culled from the Shrines of the Saints and the Gardens of the Poets by Eleanor C. Donnelly.

Pictorial Half Hours with the Saints by Auguste François Lecanu.

Victories of the Martyrs by Saint Alphonsus Liguori.

Contemporary Hagiography

BHL, Supplement

Acta Sanctorum

Cantus: A Database for Latin Ecclesiastical Chant

Hymn by Prudentius

Art & Architecture

Index of Medieval Art

Warburg Institute Iconographic Database 

A Guide to Christian Iconography: Images, Symbols, and Texts

Medieval Religion Listserv – 2016 Dillon.

Capsella reliquiario in the Tesoro Duomo Grado, according to the IMA, saint on the right
Pala di Pellegrino II nel Duomo di Cividale, center left
second from right
Post-Biblical Saints Art Index
Saints and their Attributes

A Handbook of Christian Symbols and Stories of the Saints as Illustrated in Art by Clara Erskine Clement.

Saints and their Symbols: A Companion in the Churches and Picture Galleries of Europe by E. A. Greene.

The Saints in Art by Joseph Maria von Radowitz.

Emblems of Saints by Which They Are Distinguished in Works of Art by F. C. Husenbeth.

4 June – Saint Optatus of Milevis

Modern Hagiography

Bibliotheca Sanctorum

Martyrologium Romanum

Roman Martyrology

Sanctorale Catholicum

Lives of the Saints by Alban Butler.

Lives of the Saints by Sabine Baring-Gould.

Medieval Hagiography

Acta Sanctorum

Jerome, De viris illustribus

Writings by Saint Optatus

Against the Donatists (also)

Art & Architecture

Wikimedia Commons

Saints and their Attributes

The Saints in Art by Joseph Maria von Radowitz.

Emblems of Saints by Which They Are Distinguished in Works of Art by F. C. Husenbeth.

4 June – Saint Francesco Caracciolo

Modern Hagiography

Bibliotheca Sanctorum

Martyrologium Romanum

Roman Martyrology

Lives of the Saints by Sabine Baring-Gould.

The Liturgical Year by Dom Guéranger.

Character Calendar 

Pictorial Lives of the Saints 

La vie des saints 

La vie des saints

Miniature Lives of the Saints for Every Day in the Year

Breviarium RomanumLatin & English.

Art & Architecture

Catalogo generale dei beni culturali

BeWeB

Vatican Founder Statue

Numerous Videos from Telemolise on Villa Santa Maria and Saint Francesco Caracciolo