EXHIBIT 10.01

THIRD AMENDMENT TO PROMISSORY NOTE

RECITALS

WHEREAS, the undersigned five corporate entities (each, a "Maker;” or
collectively, “Makers”) were each co-makers of a certain Promissory Note (the
“Note”) dated June 1, 2010, in the original stated amount of $6,987,646.00, in
favor of Teton, Ltd., a Texas limited partnership (“Payee”);

WHEREAS, the Note was previously amended by Amendment to Note dated October 1,
2010 (the “First Amendment”), to eliminate the requirement for an interest
payment to be made on October 1, 2010;

WHEREAS, the Note was also amended by Second Amendment to Note dated January 1,
2011 (the “Second Amendment”), to eliminate the requirement for an interest
payment to be made on January 1, 2011;

WHEREAS, in conjunction with Pegasi Energy Resources Corporation’s engagement of
Beaufort International Associates Limited on an exclusive basis to raise funds
for the company (the “Beaufort Engagement”), Makers have requested, and Payee
has agreed under certain terms set forth herein, to further amend the Note to
(i) eliminate the April 1, 2011, interest payment, and (ii) extend the maturity
date of the Note from June 1, 2011, to June 1, 2013;

NOW, THEREFORE, in consideration of the premises and the mutual promises
contained in this Amendment, Makers and Payee hereby agree as follows:

AGREEMENT

1.           Amendments to Note.  The Note is hereby amended to eliminate the
requirement for an interest payment to be made on April 1, 2011.  The Note is
hereby further amended to extend the maturity date of the Note from June 1,
2011, to June 1, 2013.  As a result of these amendments (and except as set forth
in Paragraph 2 below), no payments are required to be made on the Note until the
extended maturity date of June 1, 2013, when all principal and accrued interest
from the date of the Note shall be due and payable.

2.           Added Event of Default.  By written notice to Pegasi Energy
Resources Corporation, a Nevada corporation f/n/a Maple Mountain Explorations
Inc. (“PERC”), Payee may at its option declare a default on the Note if PERC
does not raise funds for the company during or as a result of the Beaufort
Engagement.  In such event, Payee may accelerate the Note and exercise all
remedies for a default on the Note.

3.           Makers are responsible for all costs incurred by Payee, including
without limit reasonable attorneys’ fees, with regard to the preparation and
execution of this Amendment.

4.           The execution of this Amendment shall not be deemed to be a waiver
of any Default or Event of Default.

5.           All the terms used in this Amendment which are defined in the Note
shall have the same meaning as used in the Note, unless otherwise defined in
this Amendment.  All the terms used in this Amendment which are defined in the
Stock Pledge Agreement shall have the same meaning as used in the Stock Pledge
Agreement, unless otherwise defined in this Amendment.

6.           Makers waive, discharge, and forever release Payee, Payee's
employees, officers, directors, attorneys, stockholders, and their successors
and assigns, from and of any and all claims, causes of action, allegations or
assertions that Makers have or may have had at any time up through and including
the date of this Amendment, against any or all of the foregoing, regardless of
whether any such claims, causes of action, allegations or assertions are known
to Makers or whether any such claims, causes of action, allegations or
assertions arose as  result of Payee's actions or omissions in connection with
the Note, or any amendments, extensions or modifications thereof, or Payee's
administration of the debt evidenced by the Note or otherwise, INCLUDING ANY
CLAIMS, CAUSES OF ACTION, ALLEGATIONS OR ASSERTIONS RESULTING FROM PAYEE’S OWN
NEGLIGENCE, except and to the extent (but only to the extent) caused by Payee’s
gross negligence or willful misconduct.

7.           This Amendment is not an agreement to any further or other
amendment of the Note.

8.           Makers expressly acknowledge and agree that except as expressly
amended in this Amendment, the Note remains in full force and effect and is
ratified and confirmed.  This Amendment shall neither extinguish nor constitute
a novation of the Note or indebtedness evidenced thereby.

9.           The parties covenant and agree as follows:

(1)       The rights and obligations of the parties shall be determined solely
from the written “Loan Agreement” (as such term is defined in Section
26.02(a)(2) of the Texas Business and Commerce Code) executed and delivered in
connection with the Loan, and any oral agreements between or among the parties
are superseded by and merged into the Loan Agreement.

(2)       The Loan Agreement has not been and may not be varied by any oral
agreements or discussions that have or may occur before, contemporaneously with,
or subsequent thereto.

(3)       THE WRITTEN LOAN AGREEMENT REPRESENTS THE FINAL AGREEMENT BETWEEN THE
PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR
SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES.  THERE ARE NO UNWRITTEN ORAL
AGREEMENTS AMONG THE PARTIES.

 
 

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Executed to be effective as of April 1, 2011.
 

Makers:        Payee:            
 Pegasi Energy Resources Corporation,    
a Nevada corporation f/n/a    
Maple Mountain Explorations Inc. 
   
Teton, Ltd., a Texas limited partnership
By:Notet Corp., a Texas corporation,
its general partner
           
By:
   
By:
 
Richard Lindermanis, Senior Vice President
    W.L. Sudderth, Secretary  
 and CFO
   
 
 

Pegasi Energy Resources Corporation,
a Texas corporation (and wholly-owned
subsidiary of Pegasi Energy Resources Corporation,
a Nevada corporation f/n/a Maple Mountain Explorations Inc.)
       
 
                 
By:
       
Richard Lindermanis, Vice President
             
 
 

       

         
Pegasi Operating Inc., a Texas corporation (and wholly-owned
subsidiary of Pegasi Energy Resources Corporation,
a Texas corporation)
                 
By:
       
Richard Lindermanis, Vice President
             
 
 

                                                                     

TR Rodessa, Inc., a Texas corporation (and wholly-owned
subsidiary of Pegasi Energy Resources Corporation,
a Texas corporation)
       
 
                 
By:
       
Richard Lindermanis, Vice President
             
 
 

                                                                     

59 Disposal, Inc., a Texas corporation (and wholly-owned
subsidiary of Pegasi Energy Resources Corporation,
a Texas corporation)
       
 
                 
By:
       
Richard Lindermanis, Vice President