Simple SPARQL query

Hello everyone! 
I'm new to SPARQL, and I thought that I understand the point. But, I have
file like this one: 

@prefix protons: <http://proton.semanticweb.org/2006/05/protons#
<http://proton.semanticweb.org/2006/05/protons> > . 
@prefix protont: <http://proton.semanticweb.org/2006/05/protont#
<http://proton.semanticweb.org/2006/05/protont> > . 

<http://www.lornet.org/acm-ccs/proton#Alias_07c6001f-8f5c-49e1-ae3c-92c9121b
4297>
a protons:Alias ; 
<http://www.w3.org/2000/01/rdf-schema#label>
"Convex Programming@en" . 

<http://www.lornet.org/acm-ccs/proton#Alias_63786f1d-7b3c-4872-b4e0-8227de53
c015>
a protons:Alias ; 
<http://www.w3.org/2000/01/rdf-schema#label>
"Document and Text Processing@en" . 

<http://www.lornet.org/acm-ccs/proton#J.7.1>
a protont:Topic ; 
protons:generatedBy <http://www.lornet.org/acm-ccs/proton#TrustedSrc> ; 
protons:hasMainAlias 
<http://www.lornet.org/acm-ccs/proton#Alias_dee6eec3-b503-4d3e-a98d-ecdde5d5
ee1a> . 

<http://www.lornet.org/acm-ccs/proton#Alias_ff639082-2cc4-484e-92f7-5f0f0989
8d2d>
a protons:Alias ; 
<http://www.w3.org/2000/01/rdf-schema#label>
"Store and Forward Networks@en" . 

<http://www.lornet.org/acm-ccs/proton#Alias_7f00cebc-8828-4415-83b3-2eb53ae3
b0b6>
a protons:Alias ; 
<http://www.w3.org/2000/01/rdf-schema#label>
"Integral Equations@en" . 

<http://www.lornet.org/acm-ccs/proton#Alias_08a8af20-311b-4a43-b996-7d4a8c03
4636>
a protons:Alias ; 
<http://www.w3.org/2000/01/rdf-schema#label>
"Information Filtering@en" . 

<http://www.lornet.org/acm-ccs/proton#Alias_bb28b422-05f4-47f8-a8f5-811610a2
f77f>
a protons:Alias ; 
<http://www.w3.org/2000/01/rdf-schema#label>
"Surfac eFitting@en" . 

<http://www.lornet.org/acm-ccs/proton#Alias_8b20c6a0-1b02-4c34-bd30-740d8d15
0f30>
a protons:Alias ; 
<http://www.w3.org/2000/01/rdf-schema#label>
"Reliability,Availability and Serviceability@en" . 

<http://www.lornet.org/acm-ccs/proton#Alias_b6e48ecc-f1a9-44e6-8ff9-c8817647
765a>
a protons:Alias ; 
<http://www.w3.org/2000/01/rdf-schema#label>
"Aerospace@en" . 

and I want to read labels. But, all I got is empty string, or null value.
Could someone please write a simple query which is going to read anything
from this example? 

Thank you!